feat(gocd): add deploy-getsentry-backend-st to backend pipeline filter

[mchen-sentry]

We're bumping get-sentry backend so this should go out as well.

Please see https://github.com/getsentry/getsentry/pull/20117

[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.17%. Comparing base (f3c4004) to head (32da4b2).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #978   +/-   ##
=======================================
  Coverage   89.17%   89.17%           
=======================================
  Files         125      125           
  Lines        3899     3899           
  Branches      803      803           
=======================================
  Hits         3477     3477           
  Misses        387      387           
  Partials       35       35           

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