Don't show project limit popover when FF is disabled

What does this MR do and why?

Don't show project limit popover when group_level_dependencies_filtering FF is disabled. This fixes a regression which was mistakenly introduced by !132597 (merged). enable_project_search has also been renamed to below_project_limit to make it more clear that it is not related to feature flags.

Screenshots or screen recordings

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Before	After

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

1. Make sure group_level_dependencies_filtering feature flag is disabled.

   echo 'Feature.disable(:group_level_dependencies_filtering)' | bundle exec rails c

2. Go to a group which has multiple projects on the dependency list.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.