docs(grpc-exporters): remove 'web' as supported from README.md

[pichlermarc]

Which problem is this PR solving?

The gRPC exporters for both trace and metrics listed 'web and node' as supported targets, but only 'node' is actually supported.
This PR removes 'web' from the respective README.mds.

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

Checklist:

• Followed the style guidelines of this project
• Unit tests have been added
• Documentation has been updated

[codecov]

Codecov Report

Merging #3070 (44b9b74) into main (6eca6d4) will decrease coverage by 0.41%.
The diff coverage is n/a.

❗ Current head 44b9b74 differs from pull request most recent head 75c8e83. Consider uploading reports for the commit 75c8e83 to get more accurate results

@@            Coverage Diff             @@
##             main    #3070      +/-   ##
==========================================
- Coverage   93.08%   92.66%   -0.42%     
==========================================
  Files         188      173      -15     
  Lines        6261     5523     -738     
  Branches     1323     1175     -148     
==========================================
- Hits         5828     5118     -710     
+ Misses        433      405      -28     

Impacted Files	Coverage Δ
packages/opentelemetry-resources/karma.worker.js	0.00% <0.00%> (-100.00%)	⬇️
...kages/opentelemetry-sdk-trace-base/karma.worker.js	0.00% <0.00%> (-100.00%)	⬇️
...lemetry-resources/src/detectors/BrowserDetector.ts	53.33% <0.00%> (-46.67%)	⬇️
...lemetry-resources/src/detectors/ProcessDetector.ts	95.45% <0.00%> (-4.55%)	⬇️
...emetry-instrumentation-xml-http-request/src/xhr.ts
...-sdk-trace-web/src/enums/PerformanceTimingNames.ts
...ry-context-zone-peer-dep/src/ZoneContextManager.ts
packages/opentelemetry-sdk-trace-web/src/types.ts
...telemetry-sdk-trace-web/src/StackContextManager.ts
packages/opentelemetry-sdk-trace-web/src/utils.ts
... and 9 more

[blumamir]

Not related to this fix, but I think the wording should be "OTLP receiver" instead of "opentelemetry-collector", since the exporter can send to any OTLP compatible receiver.

[blumamir]

Probably in other packages as well. Anyway, just sharing a thought. I can open a separate PR after this one is merged.

[pichlermarc]

Yes, that makes sense. 🙂
Since this PR is already approved I can also do it in a follow-up if you like.