[FIX] Do not allow admin users edit other federated users

[MarcosSpessatto]

Proposed changes (including videos or screenshots)

Issue(s)

Steps to test or reproduce

Further comments

I haven't added tests for this endpoint change since we don't have a way to create a federated user (unless set up the whole federation) and simulate the behavior.

[codecov[bot]]

Codecov Report

Merging #26528 (35f74cb) into improve/federation-general-improvements (24ac9c4) will not change coverage. The diff coverage is n/a.

@@                           Coverage Diff                            @@
##           improve/federation-general-improvements   #26528   +/-   ##
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  Coverage                                    38.07%   38.07%           
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  Files                                          745      745           
  Lines                                        18625    18625           
  Branches                                      1412     1412           
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  Hits                                          7091     7091           
+ Misses                                       11313    11310    -3     
- Partials                                       221      224    +3     

Flag	Coverage Δ
e2e	38.07% <ø> (ø)

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