[Instrumentation.WCF] fix rpc.system tag

[Kielek]

Fixes N/A

Changes

Adjust tag to otel-spec requierments.
https://github.com/open-telemetry/opentelemetry-specification/blob/5b6d22512ef72214f7cbd52747a1fbfe49f8121f/CHANGELOG.md?plain=1#L611-L612

• Appropriate CHANGELOG.md updated for non-trivial changes
• [ ] Design discussion issue #

[CodeBlanch]

LGTM

[codecov]

Codecov Report

Merging #837 (ac6b75a) into main (3768220) will increase coverage by 0.53%.
The diff coverage is n/a.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #837      +/-   ##
==========================================
+ Coverage   77.55%   78.08%   +0.53%     
==========================================
  Files         168      177       +9     
  Lines        5243     5379     +136     
==========================================
+ Hits         4066     4200     +134     
- Misses       1177     1179       +2     

Impacted Files	Coverage Δ
...entation.AspNet/TracerProviderBuilderExtensions.cs	100.00% <0.00%> (ø)
...Implementation/AspNetInstrumentationEventSource.cs	76.92% <0.00%> (ø)
...nTelemetry.Instrumentation.AspNet/AspNetMetrics.cs	100.00% <0.00%> (ø)
...rumentation.AspNet/AspNetInstrumentationOptions.cs	100.00% <0.00%> (ø)
...ion.AspNet/Implementation/HttpInMetricsListener.cs	100.00% <0.00%> (ø)
...ry.Instrumentation.AspNet/AspNetInstrumentation.cs	100.00% <0.00%> (ø)
...umentation.AspNet/Implementation/HttpInListener.cs	88.31% <0.00%> (ø)
...mentation.AspNet/MeterProviderBuilderExtensions.cs	100.00% <0.00%> (ø)
...OpenTelemetry.Instrumentation.AspNet/SpanHelper.cs	75.00% <0.00%> (ø)
....AspNet.TelemetryHttpModule/TelemetryHttpModule.cs	5.40% <0.00%> (+5.40%)	⬆️
... and 1 more