Update SDK spec to the latest W3C Baggage spec version

[lgfa29]

Fixes #2639

Changes

Update the version of the W3C Baggage spec used by the Resource SDK for the OTEL_RESOURCE_ATTRIBUTES environment variable so it matches the version used by the baggage propagation API.

The key difference is the requirement to percent-encode characters outside the baggage-octate range, and so this is now highlighted in the SDK spec.

Full diff between the latest version and the version used before:
https://github.com/w3c/baggage/compare/fdc7a5c4f4a31ba2a36717541055e551c2b032e4..main#diff-f65e951e116caf027fff48025b09977ad3539456579743d5c8018b9313484229

[lgfa29]

I wasn't sure if this could be considered a significant change, and so I didn't update the CHANGELOG.md nor spec-compliance-matrix.md. But maybe the OTEL_RESOURCE_ATTRIBUTES row in the Environment Variables section should be updated since they don't percent-decode values?

[jsuereth]

A few comments on my approval:

• I think you should update CHANGELOG.md. For spec compliance matrix
• I think you should ping maintainers to see if they need to update their compliance around parsing this attribute.
• I do not think existing usage of OTEL_RESOURCE_ATTRIBUTES will be affected at all by this specification change, even though it's more restrictive. The way I read the differences is that previously behavior was pretty unclear for these extended characters.

[lgfa29]

Thanks @jsuereth!

I think you should update CHANGELOG.md. For spec compliance matrix

I pushed a new commit with a CHANGELOG entry. I wasn't sure where to add it, so I placed it under the Resource section, but let me know if it should go somewhere else.

I think you should ping maintainers to see if they need to update their compliance around parsing this attribute.

I'm not sure who the maintainers are, so I will open an issue on each SDK repo and link back to this PR to help maintainers keep track of the changes necessary for their own project.

[github-actions]

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