fix #530 Property Actions Menu: Make it go on top

[mlukasz7]

Property Actions Menu goes on top of Property Editors and other things.

Description

Change the z-index to visually appear menu on top.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Chore (minor updates related to the tooling or maintenance of the repository, do not impact compiled assets)

Motivation and context

Fix issue #530.

How to test?

Currently, it was visible on a small screen, but in case of more options bottom element like input menu would be under the input.

Screenshots

Before:

After fix:

Checklist

• If my change requires a change to the documentation, I have updated the documentation in this pull request.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.

[nielslyngsoe]

Looks good, thanks!