Bump max length for installer URLs supplied in GitOps to 4000 characters

[iansltx]

For #24917. Should be worth the extra byte per row for the varchar field.

Checklist for submitter

• Changes file added for user-visible changes in changes/, orbit/changes/ or ee/fleetd-chrome/changes.
  See Changes files for more information.
• Added/updated tests
• If database migrations are included, checked table schema to confirm autoupdate
• For database migrations:
  • Checked schema for all modified table for columns that will auto-update timestamps during migration.
  • Confirmed that updating the timestamps is acceptable, and will not cause unwanted side effects.
  • Ensured the correct collation is explicitly set for character columns (COLLATE utf8mb4_unicode_ci).
• Manual QA for all new/changed functionality

[codecov]

Codecov Report

Attention: Patch coverage is 66.66667% with 5 lines in your changes missing coverage. Please review.

Project coverage is 63.59%. Comparing base (b5d17fc) to head (e3a66bb).
Report is 5 commits behind head on main.

Files with missing lines	Patch %	Lines
...rations/tables/20241219180042_LongInstallerURLs.go	61.53%	4 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #24942      +/-   ##
==========================================
+ Coverage   63.57%   63.59%   +0.02%     
==========================================
  Files        1604     1605       +1     
  Lines      152040   152053      +13     
  Branches     3871     3871              
==========================================
+ Hits        96656    96695      +39     
+ Misses      47684    47660      -24     
+ Partials     7700     7698       -2     

Flag	Coverage Δ
backend	64.39% <66.66%> (+0.02%)	⬆️

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[lucasmrod]

LGTM!