[DOC] Fix outdated community membership link

[opentelemetrybot]

See open-telemetry/community#2830 for details (missed this on the first round)

[netlify]

✅ Deploy Preview for opentelemetry-cpp-api-docs canceled.

Name	Link
🔨 Latest commit	c9ef12d
🔍 Latest deploy log	https://app.netlify.com/projects/opentelemetry-cpp-api-docs/deploys/685dcedd577cfa000882d97e

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.95%. Comparing base (4b5f081) to head (c9ef12d).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3500   +/-   ##
=======================================
  Coverage   89.95%   89.95%           
=======================================
  Files         219      219           
  Lines        7051     7051           
=======================================
  Hits         6342     6342           
  Misses        709      709           

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