[gha] Add conditional checks for GCP upload step

[sjchmiela]

It takes a minute https://github.com/expo/eas-cli/actions/runs/20850818613/job/59905175877?pr=3286 and is unnecessary unless the other step runs too

[github-actions]

Size Change: +2.68 kB (+0.01%)

Total Size: 53.3 MB

Filename	Size	Change
./packages/eas-cli/dist/eas-linux-x64.tar.gz	53.3 MB	+2.68 kB (+0.01%)

_{compressed-size-action}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 49.61%. Comparing base (3a7182b) to head (d2890e8).
⚠️ Report is 4 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3297   +/-   ##
=======================================
  Coverage   49.61%   49.61%           
=======================================
  Files         671      671           
  Lines       27972    27972           
  Branches     5780     5780           
=======================================
  Hits        13876    13876           
  Misses      12906    12906           
  Partials     1190     1190           

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[github-actions]

⏩ The changelog entry check has been skipped since the "no changelog" label is present.

[sjchmiela]

Will include in #3303