SUP-1886-update veracode retry on 504

[effany]

This PR updates Veracode retry handling for 504 Gateway Timeout responses.

When a request to Veracode returns HTTP 504, the connector now retries the request up to 2 times, with a fixed 30-second interval between attempts.

This change improves resiliency against temporary Veracode-side timeouts while keeping retry behavior controlled and predictable.

https://kennasecurity.atlassian.net/jira/software/c/projects/SUP/boards/58?selectedIssue=SUP-1886

[codecov]

Codecov Report

❌ Patch coverage is 62.50000% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 35.61%. Comparing base (119038c) to head (c437ea1).

Files with missing lines	Patch %	Lines
...ors/veracode_asset_vulns/lib/veracode_av_client.rb	28.57%	5 Missing ⚠️
tasks/connectors/veracode/lib/veracode_client.rb	66.66%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #614      +/-   ##
==========================================
+ Coverage   35.56%   35.61%   +0.04%     
==========================================
  Files         128      128              
  Lines        8463     8469       +6     
==========================================
+ Hits         3010     3016       +6     
  Misses       5453     5453              

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