[chore] adjust rpc attribute notes

[thompson-tomo]

Fixes #

Changes

Removes the rpc.service & rpc.method notes as they are now explicitly on the spans.

Note: if the PR is touching an area that is not listed in the existing areas, or the area does not have sufficient domain experts coverage, the PR might be tagged as experts needed and move slowly until experts are identified.

Merge requirement checklist

• CONTRIBUTING.md guidelines followed.
• Change log entry added, according to the guidelines in When to add a changelog entry.
  • If your PR does not need a change log, start the PR title with [chore]
• Links to the prototypes or existing instrumentations (when adding or changing conventions)

[thompson-tomo]

Blocked by #2503