[REMOVAL] Header files semantic_conventions.h

[marcalff]

The following files:

• api/include/opentelemetry/trace/semantic_conventions.h
• sdk/include/opentelemetry/sdk/resource/semantic_conventions.h

are deprecated, replaced by new headers, organized by semantic conventions group.

The removal date is planned for July 1, 2025.

See file DEPRECATED.md for how to migrate.

[github-actions]

This issue was marked as stale due to lack of activity.