[frontend] Fix Mitre Att&ck Coverage display on Firefox

[isselparra]

Close #1435

Proposed changes

• Remove experimental attributes since non compatible with Firefox

Checklist

• I consider the submitted work as finished
• I tested the code for its functionality

Before (Firefox):

After (Firefox):

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 32.55%. Comparing base (c04a750) to head (ab320fa).

Additional details and impacted files

@@            Coverage Diff            @@
##             master    #1484   +/-   ##
=========================================
  Coverage     32.55%   32.55%           
  Complexity     1464     1464           
=========================================
  Files           534      534           
  Lines         13766    13766           
  Branches        824      824           
=========================================
  Hits           4482     4482           
  Misses         9075     9075           
  Partials        209      209           

Flag	Coverage Δ
	32.55% <ø> (ø)

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