[backend] Fix broken migrations (#16101)

[fellowseb]

Proposed changes

Fixes broken migrations after regression in introduced in 1dffd90#diff-3db2f43c3870850bea7900ca81462ccb140015fc627df8b438d7135fa0b87912R3943.

Related issues

• Fixes Legacy tokens migration broken #16101

Checklist

• I consider the submitted work as finished
• I tested the code for its functionality
• I wrote test cases for the relevant uses case (coverage and e2e)
• I added/update the relevant documentation (either on github or on notion)
• Where necessary I refactored code to improve the overall quality

Further comments

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 35.71%. Comparing base (0adbde1) to head (910d50b).

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #16102      +/-   ##
==========================================
- Coverage   35.71%   35.71%   -0.01%     
==========================================
  Files        3232     3232              
  Lines      221682   221682              
  Branches    41430    41429       -1     
==========================================
- Hits        79169    79166       -3     
- Misses     142513   142516       +3     

Flag	Coverage Δ
opencti-client-python	46.36% <ø> (ø)
opencti-front	3.98% <ø> (ø)
opencti-graphql	72.77% <ø> (-0.01%)	⬇️

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