Removed not used file from OTLP project

[Kielek]

Towards #3421 (comment)

Cleanup projects before split to HTTP and gRPC.

Changes

Please provide a brief description of the changes here.

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

• [ ] Appropriate CHANGELOG.md updated for non-trivial changes
• [ ] Design discussion issue #
• [ ] Changes in public API reviewed

[codecov]

Codecov Report

Merging #4280 (03e5c05) into main (f3dab75) will decrease coverage by 0.04%.
The diff coverage is n/a.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4280      +/-   ##
==========================================
- Coverage   84.31%   84.28%   -0.04%     
==========================================
  Files         296      296              
  Lines       11791    11791              
==========================================
- Hits         9942     9938       -4     
- Misses       1849     1853       +4     

Impacted Files	Coverage Δ
...tation/OpenTelemetryProtocolExporterEventSource.cs	85.00% <0.00%> (-15.00%)	⬇️
...porter.OpenTelemetryProtocol/OtlpMetricExporter.cs	72.72% <0.00%> (-13.64%)	⬇️
...p/Implementation/HttpInstrumentationEventSource.cs	76.00% <0.00%> (+4.00%)	⬆️
...lementation/SqlClientInstrumentationEventSource.cs	75.00% <0.00%> (+4.16%)	⬆️

[pellared]