FIX / User update imports failing due to cookie_token overflow

[Mary-Clb]

• I have performed a self-review of my code.
• I have added tests (when available) that prove my fix is effective or that my feature works.
• I have updated the CHANGELOG with a short functional description of the fix or new feature.
• This change requires a documentation update.

Description

• It fixes !43800
• When importing updates for User records multiple times, the second run could fail with:
  Data too long for column cookie_token.During update, token fields already stored in DB were included again in the update payload.
  GLPI encrypts those token fields during update, so already-encrypted values were encrypted again, increasing size until cookie_token exceeded column capacity.
  This issue is already fixed in the GLPI 11 compatible line via PR Fix - User field updates and email import #566 , included in the 2.15.x series.
  This PR brings the same protection to the GLPI 10 compatible branch.