doc: add gRPC steps to storage quickstart

[coryan]

This change is 

[google-cloud-cpp-bot]

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For commit: 2b43eb716ee4ffca9eddc563979ed50ee1c22c71

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[codecov]

Codecov Report

Merging #7358 (2b43eb7) into main (f73e933) will decrease coverage by 0.00%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #7358      +/-   ##
==========================================
- Coverage   93.63%   93.63%   -0.01%     
==========================================
  Files        1349     1349              
  Lines      117062   117062              
==========================================
- Hits       109608   109607       -1     
- Misses       7454     7455       +1     

Impacted Files	Coverage Δ
google/cloud/grpc_error_delegate.cc	95.83% <0.00%> (-4.17%)	⬇️
...le/cloud/spanner/database_admin_connection_test.cc	99.20% <0.00%> (-0.50%)	⬇️
...cloud/pubsub/internal/subscription_session_test.cc	98.00% <0.00%> (+0.24%)	⬆️
google/cloud/bigtable/async_read_stream_test.cc	97.99% <0.00%> (+0.66%)	⬆️
...bigtable/examples/bigtable_hello_instance_admin.cc	83.51% <0.00%> (+2.19%)	⬆️

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