chore(release): change release.sh to use gh instead of hub

[devjgm]

Fixes: #6682

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This change is 

[google-cloud-cpp-bot]

Google Cloud Build Logs
For commit: e3d5fd7c4e2b3828d3de6a847e80937ce8120692

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[codecov]

Codecov Report

Merging #7071 (003dbd1) into main (52f263d) will decrease coverage by 0.00%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #7071      +/-   ##
==========================================
- Coverage   94.48%   94.48%   -0.01%     
==========================================
  Files        1304     1304              
  Lines      112377   112377              
==========================================
- Hits       106175   106174       -1     
- Misses       6202     6203       +1     

Impacted Files	Coverage Δ
google/cloud/grpc_error_delegate.cc	95.83% <0.00%> (-4.17%)	⬇️
...le/cloud/internal/default_completion_queue_impl.cc	97.00% <0.00%> (-0.60%)	⬇️
google/cloud/pubsub/samples/samples.cc	91.67% <0.00%> (-0.08%)	⬇️
...cloud/pubsub/internal/subscription_session_test.cc	98.02% <0.00%> (+0.24%)	⬆️
...torage/examples/storage_service_account_samples.cc	97.64% <0.00%> (+1.17%)	⬆️

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[google-cloud-cpp-bot]

Google Cloud Build Logs
For commit: 003dbd1cb589dd88824fb82e53c345babc646668

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[coryan]

FYI: I am not sure the line between #!/bin/bash and the Copyright notice is needed, in fact, we do have many files that do not have it. Your call.

[devjgm]

I never noticed that inconsistency before. It looks like we have 80 shell scripts total, 54 use a blank line, 26 do not. Not sure which way we prefer, but I'd be happy to clean it up in a separate PR. I don't have a strong preference which way we go... well, https://google.github.io/styleguide/shellguide.html#file-header implies a blank line may be preferred, so maybe that's a nudge.

[coryan]

SGTM, don't forget the .py files.