opentelemetry-proto: bump maximum supported protobuf version to 7.x.x

[herin049]

Description

Bumps the maximum supported protobuf to 7.x.x. Per the protobuf docs:

Since the 3.20.0 release, the Protobuf Python generated code became a thin wrapper around an embedded FileDescriptorProto. Because these protos are supported on extremely long timeframes, our usual major version compatibility windows aren’t typically necessary.

Python may break generated code compatibility in specific future major version releases, but it will be coupled with poison pill warnings and errors in advance. As of 6.32.0, all generated code since 3.20.0 will be supported until at least 8.x.y.

This change should be safe to make.

Fixes #5205

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

How Has This Been Tested?

Tox

Does This PR Require a Contrib Repo Change?

• Yes. - Link to PR:
• No.

Checklist:

• Followed the style guidelines of this project
• Changelogs have been updated