Update CHANGELOG.md for 12.8.0

[ci skip]

changelogs/unreleased/198460-date-time-picker-custom-dates-make-the-date-field-too-long-truncat.yml

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-title: Add tooltip when dates in date picker are too long
-merge_request: 24664
-author:
-type: added

changelogs/unreleased/198464-add-can_create_merge_request_in-to-project-api-response.yml

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-title: Add can_create_merge_request_in to /project/:id API response
-merge_request: 23577
-author:
-type: added

changelogs/unreleased/198466.yml

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-title: update service desk project to use GlLoadingIcon over font awesome spinner
-merge_request:
-author: Oregand
-type: changed

changelogs/unreleased/198480-share_groups_with_groups_fix_owner_access.yml

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-title: Allow Owner access level for sharing groups with groups
-merge_request: 23868
-author:
-type: fixed

changelogs/unreleased/198577-fix-emails-on-push.yml

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-title: Fix emails on push integrations created before 12.7
-merge_request: 23699
-author:
-type: fixed

changelogs/unreleased/198621-actionview-template-error-missing-partial-notify-links-projects-ge.yml

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-title: Fix Pipeline failed notification email not being delivered if the failed job
-  is a bridge job
-merge_request: 23668
-author:
-type: fixed

changelogs/unreleased/198652-update-index-on-license-scanning.yml

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-title: Include license_scanning to index_ci_builds_on_name_for_security_products_values
-merge_request: 24090
-author:
-type: changed

changelogs/unreleased/198655-lowercase-operator.yml

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-title: Switch dropdown operators to lowercase
-merge_request:
-author:
-type: other

changelogs/unreleased/199034-nomethoderror-undefined-method-unsubscribe-for-nil-nilclass.yml

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-title: Fix 500 error when trying to unsubscribe from an already deleted entity
-merge_request: 23747
-author:
-type: fixed

changelogs/unreleased/199060-fix-snippet-search-results.yml

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-title: Fix design of snippet search results page
-merge_request: 23780
-author:
-type: fixed

changelogs/unreleased/199211-fix-user-popover-glitch.yml

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-title: Fix user popover glitch
-merge_request: 23904
-author:
-type: fixed

changelogs/unreleased/199257-renamemove-webide-dropdown.yml

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-title: "Change `Rename` to `Rename/Move` in Web IDE Dropdown"
-merge_request: 23877
-author:
-type: added

changelogs/unreleased/199526-new-mr-changes-tab-edit-file-button-ui-polish.yml

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-title: Remove gray color from diff buttons
-merge_request: 24041
-author:
-type: fixed

changelogs/unreleased/199698-smart-member-suggestions.yml

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-title: Make smarter user suggestions for assign slash commands
-merge_request: 24294
-author:
-type: added

changelogs/unreleased/200011-move-error-tracking-incidents-to-core.yml

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-title: Move Settings->Operations->Incidents to the Core
-merge_request: 24600
-author:
-type: changed

changelogs/unreleased/20042-create-lfs-objects-project.yml

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-title: Create LfsObjectsProject record for forks as well
-merge_request: 22418
-author:
-type: fixed

changelogs/unreleased/201743-avoid-loading-user-activity-calendar-data-on-mobile.yml

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-title: Avoid loading user activity calendar on mobile
-merge_request: 24277
-author: Takuya Noguchi
-type: fixed

changelogs/unreleased/201761-design-discussion-note-preview-is-broken.yml

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-title: Resolve Design discussion note preview is broken
-merge_request: 24288
-author:
-type: fixed

changelogs/unreleased/201893-resolve-soft-email-confirmation-flow.yml

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-title: Allow a grace period for new users to confirm their email
-merge_request: 24371
-author:
-type: added

changelogs/unreleased/201910-cannot-find-projects-within-subgroups-when-you-select-a-top-level-.yml

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-title: Query projects of subgroups in Cycle Analytics
-merge_request: 24392
-author:
-type: fixed