Revert the workaround for < .NET Core 3.1

Author: andrewlock

tracer/src/Datadog.Trace/ClrProfiler/AutoInstrumentation/RabbitMQ/BasicPublishAsyncCachedStringsIntegration.cs

@@ -41,23 +41,12 @@ internal static CallTargetState OnMethodBegin<TTarget, TExchange, TRoutingKey, T
         return BasicPublishAsyncIntegration.OnMethodBegin(instance, exchangeString, routingKeyString, mandatory, basicProperties, body, default);
     }
 
-#if NETCOREAPP3_1_OR_GREATER
     // We don't support ValueTask in < .NET Core 3.1, which means this doesn't work and is never called
     internal static TReturn? OnAsyncMethodEnd<TTarget, TReturn>(TTarget instance, TReturn? returnValue, Exception? exception, in CallTargetState state)
     {
         state.Scope.DisposeWithException(exception);
         return returnValue;
     }
-#else
-    // If the method executes synchronously, then this works fine, but if it executes asynchronously we could miss the exception
-    // This is because the exception is thrown after the method returns, and we can't catch it here
-    // If/when we support handling ValueTask correctly in < .NET Core 3.1, we should remove this method
-    internal static CallTargetReturn<TReturn?> OnMethodEnd<TTarget, TReturn>(TTarget instance, TReturn? returnValue, Exception? exception, in CallTargetState state)
-    {
-        state.Scope.DisposeWithException(exception);
-        return new CallTargetReturn<TReturn?>(returnValue);
-    }
-#endif
 }
 
 /// <summary>

tracer/src/Datadog.Trace/ClrProfiler/AutoInstrumentation/RabbitMQ/BasicPublishAsyncIntegration.cs

@@ -65,21 +65,10 @@ internal static CallTargetState OnMethodBegin<TTarget, TBasicProperties, TBody>(
         return new CallTargetState(scope);
     }
 
-#if NETCOREAPP3_1_OR_GREATER
     // We don't support ValueTask in < .NET Core 3.1, which means this doesn't work and is never called
     internal static TReturn? OnAsyncMethodEnd<TTarget, TReturn>(TTarget instance, TReturn? returnValue, Exception? exception, in CallTargetState state)
     {
         state.Scope.DisposeWithException(exception);
         return returnValue;
     }
-#else
-    // If the method executes synchronously, then this works fine, but if it executes asynchronously we could miss the exception
-    // This is because the exception is thrown after the method returns, and we can't catch it here
-    // If/when we support handling ValueTask correctly in < .NET Core 3.1, we should remove this method
-    internal static CallTargetReturn<TReturn?> OnMethodEnd<TTarget, TReturn>(TTarget instance, TReturn? returnValue, Exception? exception, in CallTargetState state)
-    {
-        state.Scope.DisposeWithException(exception);
-        return new CallTargetReturn<TReturn?>(returnValue);
-    }
-#endif
 }