ETQ tech - fix tasks pour backfill les notifications de type nouveauté

[Benoit-MINT]

fix #11680
car on peut avoir dans follow des instructeurs qui n'existent plus

[codecov]

Codecov Report

Attention: Patch coverage is 75.00000% with 1 line in your changes missing coverage. Please review.

Project coverage is 73.10%. Comparing base (32d1338) to head (1126f40).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
...er_notification_for_annotation_instructeur_task.rb	0.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##             main   #11684       +/-   ##
===========================================
+ Coverage   58.55%   73.10%   +14.54%     
===========================================
  Files        1263     1263               
  Lines       27768    27772        +4     
  Branches     5709     5713        +4     
===========================================
+ Hits        16260    20303     +4043     
+ Misses      11508     7469     -4039     

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