[FIX] Unable to remove a user who joined a public team with a mention

[LucianoPierdona]

Proposed changes (including videos or screenshots)

This PR fixes a bug where a user that joins a team by mention don't get added to the team.

Issue(s)

Fix #25817

Steps to test or reproduce

1. Go to the team creation menu. Switch the private setting to off. Create a team.
2. Mention user with @. The user is added.
3. Remove user from the team.
4. The user is not deleted. A Bad Request error appears.

Further comments

[codecov]

Codecov Report

Merging #26218 (a568881) into develop (1928374) will increase coverage by 0.05%.
The diff coverage is n/a.

❗ Current head a568881 differs from pull request most recent head d157c10. Consider uploading reports for the commit d157c10 to get more accurate results

@@             Coverage Diff             @@
##           develop   #26218      +/-   ##
===========================================
+ Coverage    38.60%   38.65%   +0.05%     
===========================================
  Files          758      758              
  Lines        18820    18816       -4     
  Branches      1452     1459       +7     
===========================================
+ Hits          7266     7274       +8     
+ Misses       11334    11322      -12     
  Partials       220      220              

Flag	Coverage Δ
e2e	38.65% <ø> (+0.05%)	⬆️

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