Fix: Render flat list for groups when filtering

[ChrisHuynh333]

What does this PR do and why?

This PR fixes a bug where the expected flat list when filtering for groups (on dashboard and subgroups/projects) was not rendering properly.

Screenshots or screen recordings

Before:

Now:

How to set up and validate locally

On both dashboard groups and groups subgroups and projects

1. Use the search bar to filter down the list (filter with an overlapping name a group(s) and their subgroup(s)).
2. Verify any groups that would have subgroups no longer has the dropdown to view its subgroups within, and that any subgroups that fit the filter are now listed.

PR 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 PR acceptance checklist for this PR.

[github-actions]

Code Metrics Report

Coverage	Test Execution Time
93.3%	8m10s

Code coverage of files in pull request scope (92.5%)

Files	Coverage
app/controllers/dashboard/groups_controller.rb	100.0%
app/controllers/groups_controller.rb	89.3%
app/views/groups/subgroups/_index.html.erb	100.0%

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Reported by octocov

[joshsadam]

Looks great to me, thanks for fixing the bug I introduced.

[deepsidhu85]

Looks good to me!