Remove the option of using grpcio for gRPC

[djc]

Fixes #1524

Merge requirement checklist

• CONTRIBUTING guidelines followed
• Unit tests added/updated (if applicable)
• Appropriate CHANGELOG.md files updated for non-trivial, user-facing changes
• Changes in public API reviewed (if applicable)

[codecov]

Codecov Report

Attention: 6 lines in your changes are missing coverage. Please review.

Comparison is base (8688e7e) 61.8% compared to head (dad855e) 65.5%.
Report is 12 commits behind head on main.

Files	Patch %	Lines
opentelemetry-sdk/src/metrics/periodic_reader.rs	92.1%	4 Missing ⚠️
opentelemetry-sdk/src/logs/log_emitter.rs	90.9%	1 Missing ⚠️
opentelemetry/src/logs/noop.rs	0.0%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #1534     +/-   ##
=======================================
+ Coverage   61.8%   65.5%   +3.6%     
=======================================
  Files        144     140      -4     
  Lines      19810   19569    -241     
=======================================
+ Hits       12256   12824    +568     
+ Misses      7554    6745    -809     

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[shaun-cox]

Thanks for doing this!

[cijothomas]

LGTM.
Can you add an entry in changelog.md for the opentelemetry-otlp

[djc]

Added changelog entries in -proto and -otlp.