Fix a typo in DerivedConformances

Author: noahsark769

lib/Sema/DerivedConformances.cpp

@@ -63,7 +63,7 @@ bool DerivedConformance::derivesProtocolConformance(TypeChecker &tc,
         }
 
         // hasOnlyCasesWithoutAssociatedValues will return true for empty enums;
-        // empty enumas are allowed to conform as well.
+        // empty enums are allowed to conform as well.
         return enumDecl->hasOnlyCasesWithoutAssociatedValues();
       }