chore: drop column only if exists

[cisse21]

Description

Drop Column only if it exists in reports migration

Notion Ticket

https://www.notion.so/rudderstacks/8aac9087df644365acdf64e28e290153?v=6e06b0a5ade24f0aa5ffe05dc2972e84&p=94f69f8b3ab84461adf0aab881da2cde&pm=s

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

Base: 52.20% // Head: 52.21% // Increases project coverage by +0.00% 🎉

Coverage data is based on head (47dad38) compared to base (d1d2338).
Patch has no changes to coverable lines.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #2979   +/-   ##
=======================================
  Coverage   52.20%   52.21%           
=======================================
  Files         328      328           
  Lines       51468    51468           
=======================================
+ Hits        26870    26872    +2     
  Misses      22978    22978           
+ Partials     1620     1618    -2     

Impacted Files	Coverage Δ
...rvices/streammanager/kafka/client/testutil/util.go	66.99% <0.00%> (-3.89%)	⬇️
router/router.go	76.71% <0.00%> (-0.19%)	⬇️
jobsdb/migration.go	77.06% <0.00%> (+0.77%)	⬆️
config/backend-config/namespace_config.go	70.00% <0.00%> (+3.00%)	⬆️
router/manager/manager.go	100.00% <0.00%> (+3.29%)	⬆️

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