Update CHANGELOG.md for 10.4.0

[ci skip]

changelogs/unreleased/40274-user-settings-breadcrumbs.yml

----
-title: Fix breadcrumbs in User Settings
-merge_request: 16172
-author: rfwatson
-type: fixed

changelogs/unreleased/40301-rebase.yml

----
-title: Allow user to rebase merge requests.
-merge_request:
-author:
-type: added

changelogs/unreleased/40418-migrate-existing-data-from-kubernetesservice-to-clusters-platforms-kubernetes.yml

----
-title: Migrate existing data from KubernetesService to Clusters::Platforms::Kubernetes
-merge_request: 15589
-author:
-type: changed

changelogs/unreleased/40453-fix-api-endpoints-to-edit-wiki-pages-where-project-belongs-to-a-group.yml

----
-title: Fix API endpoints to edit wiki pages where project belongs to a group
-merge_request: 16170
-author:
-type: fixed

changelogs/unreleased/40509_sorting_tags_api.yml

----
-title: add support for sorting in tags api
-merge_request: 15772
-author: haseebeqx
-type: added

changelogs/unreleased/40533-groups-tree-updates.yml

----
-title: Update groups tree to use GitLab SVG icons, add last updated at information
-  for projects
-merge_request: 15980
-author:
-type: changed

changelogs/unreleased/40549-render-emoj-in-groups-overview.yml

----
-title: Rendering of emoji's in Group-Overview
-merge_request: 16098
-author: Jacopo Beschi @jacopo-beschi
-type: added

changelogs/unreleased/40622-use-left-right-and-max-count.yml

----
-title: Improve the performance for counting diverging commits. Show 999+
-  if it is more than 1000 commits
-merge_request: 15963
-author:
-type: performance

changelogs/unreleased/40780-choose-file.yml

----
-title: Update Browse file to Choose file in all occurences
-merge_request:
-author:
-type: other

changelogs/unreleased/40871-todo-notification-count-shows-notification-without-having-a-todo.yml

----
-title: Reset todo counters when the target is deleted
-merge_request: 15807
-author:
-type: fixed

changelogs/unreleased/40895-fix-frequent-projects-stale-path.yml

----
-title: Use relative URL for projects to avoid storing domains
-merge_request: 15876
-author:
-type: fixed

changelogs/unreleased/41016-import-gitlab-shell-projects.yml

----
-title: Import some code and functionality from gitlab-shell to improve subprocess
-  handling
-merge_request:
-author:
-type: other

changelogs/unreleased/41053-extend-cluster-applications-to-allow-install-to-prometheus.yml

----
-title: Add Prometheus to available Cluster applications
-merge_request: 15895
-author:
-type: added

changelogs/unreleased/41054-disable-creation-of-new-kubernetes-integrations.yml

----
-title: Disable creation of new Kubernetes Integrations unless they're active or created
-  from template
-merge_request: 41054
-author:
-type: added

changelogs/unreleased/41056-create-cluster-from-kubernetes-integration-application-template.yml

----
-title: Allow automatic creation of Kubernetes Integration from template
-merge_request: 16104
-author:
-type: added

changelogs/unreleased/41244-issue-board-shortcut-working-while-no-issues.yml

----
-title: disables shortcut to issue boards when issues are not enabled
-merge_request: 16020
-author: Christiaan Van den Poel
-type: fixed

changelogs/unreleased/41249-clearing-the-cache.yml

----
-title: Implement project jobs cache reset
-merge_request: 16067
-author:
-type: added

changelogs/unreleased/41268-bump-ruby-to-2-3-6.yml

----
-title: Upgrade Ruby to 2.3.6 to include security patches
-merge_request: 16016
-author:
-type: security

changelogs/unreleased/41424-gitlab-rake-gitlab-import-repos-schedules-an-import.yml

----
-title: Fix gitlab-rake gitlab:import:repos import schedule
-merge_request: 16115
-author:
-type: fixed

changelogs/unreleased/41468-error-500-trying-to-view-a-merge-request-json-undefined-method-binary-for-nil-nilclass.yml

----
-title: Fix viewing merge request diffs where the underlying blobs are unavailable
-merge_request:
-author:
-type: fixed