Fix visibility filter on explore projects

What does this MR do?

On the Explore projects page (URL: <base URL>/explore), you can filter the projects list by visibility (Any, Private, Internal, Public). This filter does not work as intended for the selection Internal: Instead of the internal projects, no projects are returned and displayed at all.

This ~bug is fixed by this MR.

🛠 with ❤ at Siemens

/cc @bufferoverflow

Screenshots

before & after MR: Initial list (unfiltered)	before MR: filtered by Visibility: Internal	after MR: filtered by Visibility: Internal

Does this MR meet the acceptance criteria?

Conformity

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• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• [-] Tested in all supported browsers
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