[frontend]Fix users list header

[johanah29]

#892

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 26.85%. Comparing base (2a7bfc4) to head (50fca45).
Report is 17 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master     #873      +/-   ##
============================================
- Coverage     26.97%   26.85%   -0.12%     
- Complexity      913      914       +1     
============================================
  Files           410      410              
  Lines          9280     9339      +59     
  Branches        431      439       +8     
============================================
+ Hits           2503     2508       +5     
- Misses         6717     6771      +54     
  Partials         60       60              

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[RomuDeuxfois]

what is the purpose of this fix?
If the goal is to center the admin icon, we have to think about what else you want to center: the headers, ect.
My concern is about adding a padding instead of have a generic flex class

Review adressed