Remove redundant macro check in nostd::shared_ptr

[ThomsonTan]

Fixes # (issue)

Changes

Please provide a brief description of the changes here.

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

[marcalff]

LGTM

[codecov]

Codecov Report

Merging #1939 (dd1ddab) into main (52309dd) will decrease coverage by 0.02%.
The diff coverage is n/a.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1939      +/-   ##
==========================================
- Coverage   87.12%   87.10%   -0.02%     
==========================================
  Files         165      165              
  Lines        4596     4596              
==========================================
- Hits         4004     4003       -1     
- Misses        592      593       +1     

Impacted Files	Coverage Δ
api/include/opentelemetry/nostd/shared_ptr.h	100.00% <ø> (ø)
sdk/src/trace/batch_span_processor.cc	90.70% <0.00%> (-0.77%)	⬇️