[BUILD] enum CanonicalCode names too generic... conflict with old C defines

[marcalff]

Fixes #2384

Changes

Please provide a brief description of the changes here.

• Removed unused header file api/include/opentelemetry/trace/canonical_code.h

This header file is no longer used, and causes collisions in user space with ASN1, on C defines.

For significant contributions please make sure you have completed the following items:

• CHANGELOG.md updated for non-trivial changes
• Unit tests have been added
• Changes in public API reviewed

[codecov]

Codecov Report

Merging #2385 (b760678) into main (f16deb0) will not change coverage.
Report is 1 commits behind head on main.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main    #2385   +/-   ##
=======================================
  Coverage   87.43%   87.43%           
=======================================
  Files         199      199           
  Lines        6030     6030           
=======================================
  Hits         5272     5272           
  Misses        758      758           

Files	Coverage Δ
api/include/opentelemetry/trace/span.h	84.22% <ø> (ø)
...de/opentelemetry/exporters/ostream/span_exporter.h	100.00% <ø> (ø)

[lalitb]

LGTM. Hopefully, no one was taking dependency on this header file for their own purpose. Good to mention that as breaking change just to be safe :)

[marcalff]

LGTM. Hopefully, no one was taking dependency on this header file for their own purpose. Good to mention that as breaking change just to be safe :)

Good point, thanks.

Fixed in CHANGELOG.