chore(examples/koa): use exported strings for attributes

[maryliag]

Which problem is this PR solving?

• Part Of Update usage of semantic conventions to new exported strings #2025

Short description of the changes

On package examples/koa:

• Update @opentelemetry/semantic-conventions ^1.23.0
• Use exported strings for Semantic Attributes.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.34%. Comparing base (dfb2dff) to head (8f67c61).
Report is 81 commits behind head on main.

❗ Current head 8f67c61 differs from pull request most recent head de19df7. Consider uploading reports for the commit de19df7 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2123      +/-   ##
==========================================
- Coverage   90.97%   90.34%   -0.63%     
==========================================
  Files         146      147       +1     
  Lines        7492     7678     +186     
  Branches     1502     1575      +73     
==========================================
+ Hits         6816     6937     +121     
- Misses        676      741      +65     

see 15 files with indirect coverage changes

[maryliag]

/easycla