docs(OpenTelemetry): update Metrics and Attributes tables

[evansims]

Description

Updates the OpenTelemetry feature documentation to use the new Metrics and Attributes tables, which include mentions of default state and grammar fixes.

References

Review Checklist

• I have clicked on "allow edits by maintainers".
• I have added documentation for new/changed functionality in this PR or in a PR to openfga.dev [Provide a link to any relevant PRs in the references section above]
• The correct base branch is being used, if not main
• I have added tests to validate that the change in functionality is working as expected

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 31.70%. Comparing base (af528e6) to head (cc978d0).

Additional details and impacted files

@@            Coverage Diff            @@
##               main     #115   +/-   ##
=========================================
  Coverage     31.70%   31.70%           
  Complexity      885      885           
=========================================
  Files           169      169           
  Lines          6309     6309           
  Branches        699      699           
=========================================
  Hits           2000     2000           
  Misses         4207     4207           
  Partials        102      102           

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