fix: fixing the z-index bug on data model page

[wrt95]

Description

• Adding higher z-index to make sure the popover opens up above the header

Related Issue(s)

• PR itself

Verification

• Your code builds clean without any errors or warnings
• Manual testing done (required)
• Relevant automated test added (if you find this hard, leave it and we'll help out)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 94.51%. Comparing base (f3053c6) to head (6d07155).
Report is 4 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #13757   +/-   ##
=======================================
  Coverage   94.51%   94.51%           
=======================================
  Files        1605     1605           
  Lines       21536    21537    +1     
  Branches     2542     2542           
=======================================
+ Hits        20355    20356    +1     
  Misses        938      938           
  Partials      243      243           

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[framitdavid]

Tested OK. I let the Github action approve this PR as well, since I did both testing and review.