chore(instrumentation-grpc): add 'grpc' deprecation notice postinstall script

[pichlermarc]

Which problem is this PR solving?

We currently have no proper way to notify users that the 'grpc' package instrumentation code is being removed from the @opentelemetry/instrumentation-grpc package. As discussed in the SIG meeting last week, since the package is not released as stable yet, increasing semver major is not an option.

Please feel free to suggest any changes to wording of the changelog/message.

Related #3780, #3807

Type of change

• 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
• None of the above?

How Has This Been Tested?

• Ran postinstall script locally

Checklist:

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

[codecov]

Codecov Report

Merging #3833 (4fe01e9) into main (0c12777) will decrease coverage by 1.23%.
The diff coverage is n/a.

❗ Current head 4fe01e9 differs from pull request most recent head 32d1195. Consider uploading reports for the commit 32d1195 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3833      +/-   ##
==========================================
- Coverage   92.95%   91.73%   -1.23%     
==========================================
  Files         297      169     -128     
  Lines        9060     4672    -4388     
  Branches     1848      927     -921     
==========================================
- Hits         8422     4286    -4136     
+ Misses        638      386     -252     

see 137 files with indirect coverage changes

[JamieDanielson]

Added a non-blocking suggestion for adding color to make it pop more, otherwise looks good to me.

[hectorhdzg]

LGTM

[JamieDanielson]

nice! definitely grabs your attention.