[RUN AS-IF-FOSS] Resolve "FOSS master failure: spec/finders/joined_groups_finder_spec.rb"

What does this MR do?

Reapply the Group.unscoped around the User#authorized_groups query to fix a FOSS spec.

Closes #281059 (closed)

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Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry
• [-] Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• [-] Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• [-] Tested in all supported browsers
• [-] Informed Infrastructure department of a default or new setting change, if applicable per definition of done