Remove unused ExecutionContext type reference (#121570)

Author: MichalStrehovsky

src/coreclr/tools/Common/JitInterface/CorInfoImpl.cs

@@ -3398,7 +3398,6 @@ private void getAsyncInfo(ref CORINFO_ASYNC_INFO pAsyncInfoOut)
             pAsyncInfoOut.continuationStateFldHnd = ObjectToHandle(continuation.GetKnownField("State"u8));
             pAsyncInfoOut.continuationFlagsFldHnd = ObjectToHandle(continuation.GetKnownField("Flags"u8));
             DefType asyncHelpers = _compilation.TypeSystemContext.SystemModule.GetKnownType("System.Runtime.CompilerServices"u8, "AsyncHelpers"u8);
-            DefType executionContext = _compilation.TypeSystemContext.SystemModule.GetKnownType("System.Threading"u8, "ExecutionContext"u8);
             pAsyncInfoOut.captureExecutionContextMethHnd = ObjectToHandle(asyncHelpers.GetKnownMethod("CaptureExecutionContext"u8, null));
             pAsyncInfoOut.restoreExecutionContextMethHnd = ObjectToHandle(asyncHelpers.GetKnownMethod("RestoreExecutionContext"u8, null));
             pAsyncInfoOut.captureContinuationContextMethHnd = ObjectToHandle(asyncHelpers.GetKnownMethod("CaptureContinuationContext"u8, null));