docs(pubsub): add cloud storage subscription sample

[alevenberg]

Part of #11720

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Here is the summary of changes.

You are about to add 1 region tag.

• google/cloud/pubsub/samples/samples.cc:435, tag pubsub_create_cloud_storage_subscription

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[coryan]

Shouldn't we run this as part of the AutoRun() function?

[alevenberg]

Added the sample to AutoRun

[codecov]

Codecov Report

Patch coverage: 81.81% and project coverage change: -0.01 ⚠️

Comparison is base (40f58f5) 93.60% compared to head (5c8dcb1) 93.60%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #12088      +/-   ##
==========================================
- Coverage   93.60%   93.60%   -0.01%     
==========================================
  Files        2012     2012              
  Lines      176155   176177      +22     
==========================================
+ Hits       164896   164907      +11     
- Misses      11259    11270      +11     

Impacted Files	Coverage Δ
google/cloud/pubsub/samples/samples.cc	87.07% <81.81%> (-0.01%)	⬇️

... and 5 files with indirect coverage changes

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