Remove changelogs we've already released in the security patches

changelogs/unreleased/29943-environment-folder.yml

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-title: Resolve CSRF token leakage via pathname manipulation on environments page
-merge_request:
-author:

changelogs/unreleased/dm-go-get-xss.yml

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-title: Fix XSS issue in go-get handling
-merge_request:
-author:

changelogs/unreleased/fix-escape-commit-block.yml

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-title: Prevent a persistent XSS in the commit author block
-merge_request:
-author:
-type: security

changelogs/unreleased/rs-issue-36098.yml

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-title: Disallow arbitrary properties in `th` and `td` `style` attributes
-merge_request:
-author:

changelogs/unreleased/rs-issue-36104.yml

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-title: Disallow the `name` attribute on all user-provided markup
-merge_request:
-author: