docs: update OpenCensus shim example for metrics

[aabmass]

Which problem is this PR solving?

Fixes #3461

Short description of the changes

Add documentation for using OpenCensus shim to pipe metrics to OTel. This is the last PR for the shim.

Type of change

Please delete options that are not relevant.

• This change requires a documentation update

How Has This Been Tested?

Added screenshots of working example

Checklist:

• Followed the style guidelines of this project
• Unit tests have been added
• Documentation has been updated

[codecov]

Codecov Report

Merging #4078 (f75f5dc) into main (be16272) will increase coverage by 0.01%.
The diff coverage is n/a.

❗ Current head f75f5dc differs from pull request most recent head 5cf9edf. Consider uploading reports for the commit 5cf9edf to get more accurate results

@@            Coverage Diff             @@
##             main    #4078      +/-   ##
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+ Coverage   92.29%   92.30%   +0.01%     
==========================================
  Files         328      328              
  Lines        9385     9385              
  Branches     1993     1993              
==========================================
+ Hits         8662     8663       +1     
+ Misses        723      722       -1     

[pichlermarc]

Looks good, thanks for updating the docs/example! 🙂