Added limitation in ot-shim readme

[mercybassey]

Which problem is this PR solving?

This PR informs users that the OpenTracing shim doesn't include a scope manager.

Fixes #2700

Short description of the changes

This PR updates the OpenTracing shim Readme.md file by adding a limitation section; informing users that the OpenTracing shim doesn't include a scope manager.

Type of change

• This change requires a documentation update

How Has This Been Tested?

No test was created/run

Checklist:

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

[mercybassey]

Hi @pichlermarc I'd appreciate your review. Thanks.

[pichlermarc]

thanks for working on this - a few suggestions as per my understanding of the issue.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 93.17%. Comparing base (006fe44) to head (2556bc8).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5072      +/-   ##
==========================================
- Coverage   93.18%   93.17%   -0.02%     
==========================================
  Files         315      315              
  Lines        8086     8086              
  Branches     1617     1617              
==========================================
- Hits         7535     7534       -1     
- Misses        551      552       +1     

see 1 file with indirect coverage changes

[mercybassey]

thanks for working on this - a few suggestions as per my understanding of the issue.

@pichlermarc I have committed your suggestions. Thanks.