chore: remove deprecated merged schema field

[cisse21]

Description

Getting rid of the deprecated mergedschema field from warehouse tables

Notion Ticket

Notion Link

Security

• The code changed/added as part of this pull request won't create any security issues with how the software is being used.

[codecov]

Codecov Report

Patch coverage has no change and project coverage change: +0.02 🎉

Comparison is base (b525949) 68.01% compared to head (b597db9) 68.03%.

❗ Current head b597db9 differs from pull request most recent head b662575. Consider uploading reports for the commit b662575 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3482      +/-   ##
==========================================
+ Coverage   68.01%   68.03%   +0.02%     
==========================================
  Files         330      330              
  Lines       53574    53560      -14     
==========================================
+ Hits        36437    36440       +3     
+ Misses      14740    14725      -15     
+ Partials     2397     2395       -2     

Impacted Files	Coverage Δ
warehouse/internal/model/upload.go	100.00% <ø> (ø)
warehouse/internal/repo/upload.go	83.29% <ø> (+0.43%)	⬆️
warehouse/upload.go	64.52% <ø> (+0.10%)	⬆️

... and 11 files with indirect coverage changes

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[lvrach]

Can we remove the column in a release/separate PR?

So we are able to revert back without manual intervention