Update CHANGELOG.md for 8.15.2

CHANGELOG.md

...logs/unreleased/25909-fix-mr-list-timestamp-alignment.yml

...released/25930-discussion-actions-overlap-header-text.yml

...request-view-crash-when-commiting-a-js-sourcemap-file.yml

...gs/unreleased/26018-mini-pipeline-hover-cross-broswer.yml

changelogs/unreleased/26026-pipeline-overflow-firefox.yml

...eleased/26038-fix-confedential-warning-text-alignment.yml

changelogs/unreleased/26040-hide-scroll-top.yml

changelogs/unreleased/auto-deploy-with-space.yml

changelogs/unreleased/changelog-mr8322.yml

changelogs/unreleased/fix-latest-pipeine-ordering.yml

changelogs/unreleased/label-gfm-error-fix.yml

changelogs/unreleased/resolve-note-svg-color.yml