Docs: Fix anchors with extra hashes

What does this MR do?

A quick MR to fix anchors that have extra hashes in them by accident.

Ported to EE in https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/9480 (please merge EE first)

Related issues

Related to https://gitlab.com/gitlab-com/gitlab-docs/merge_requests/397
Related to https://gitlab.com/gitlab-com/gitlab-docs/issues/330

Author's checklist

• Apply the correct labels and milestone
• Crosslink the document from the higher-level index
• Crosslink the document from other subject-related docs
• Feature moving tiers? Make sure the change is also reflected in features.yml
• Correctly apply the product badges and tiers
• Port the MR to EE (or backport from CE): always recommended, required when the ee-compat-check job fails

Review checklist

• Your team's review (required)
• PM's review (recommended, but not a blocker)
• Technical writer's review (required)
• Merge the EE-MR first, CE-MR afterwards