remove redundant ?? string.Empty in GetSampler (#6078)

Co-authored-by: Rajkumar Rangaraj <[email protected]>

Author: SimonCropp

src/OpenTelemetry/Trace/TracerProviderSdk.cs

@@ -440,7 +440,7 @@ private static Sampler GetSampler(IConfiguration configuration, Sampler? stateSa
                     }
 
                 default:
-                    OpenTelemetrySdkEventSource.Log.TracesSamplerConfigInvalid(configValue ?? string.Empty);
+                    OpenTelemetrySdkEventSource.Log.TracesSamplerConfigInvalid(configValue);
                     break;
             }