[Gardening] Delete this unused variable.

It's computed below.

Author: nate-chandler

lib/IRGen/GenFunc.cpp

@@ -1631,7 +1631,6 @@ class CoroPartialApplicationForwarderEmission
 
     /// Get the continuation function pointer
     ///
-    auto sig = Signature::forCoroutineContinuation(subIGF.IGM, origType);
     auto schemaAndEntity =
       getCoroutineResumeFunctionPointerAuth(subIGF.IGM, origType);
     auto pointerAuth = PointerAuthInfo::emit(subIGF, schemaAndEntity.first,