Update stale docs.gitlab.com links

Audited every hardcoded https://docs.gitlab.com URL in this repo against the current documentation site structure, and fixed the ones that were unambiguously stale:

• Dropped the .html suffix from four links to advanced-configuration.
• /development/documentation/feature-change-workflow/ is now /development/documentation/workflow/.
• /security/token_overview/ is now /security/tokens/.
• Four anchors were renamed on the target pages, so they no longer matched.

Translations under docs-locale/ and the fuzzing corpus under common/buildlogger/internal/testdata/ were left alone.

Related links

• Related to https://gitlab.com/gitlab-org/gitlab/-/issues/577350+

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