[Constrant system] Drop expression from diagnoseAmbiguityWithFixes.

It's unused now.

Author: DougGregor

lib/Sema/ConstraintSystem.cpp

@@ -2425,7 +2425,7 @@ bool ConstraintSystem::salvage(SmallVectorImpl<Solution> &viable, Expr *expr) {
 
     // Before removing any "fixed" solutions, let's check
     // if ambiguity is caused by fixes and diagnose if possible.
-    if (diagnoseAmbiguityWithFixes(expr, viable))
+    if (diagnoseAmbiguityWithFixes(viable))
       return true;
 
     // FIXME: If we were able to actually fix things along the way,
@@ -2529,7 +2529,7 @@ static void diagnoseOperatorAmbiguity(ConstraintSystem &cs,
 }
 
 bool ConstraintSystem::diagnoseAmbiguityWithFixes(
-    Expr *expr, ArrayRef<Solution> solutions) {
+    ArrayRef<Solution> solutions) {
   if (solutions.empty())
     return false;
 

lib/Sema/ConstraintSystem.h

@@ -2108,7 +2108,7 @@ class ConstraintSystem {
   void diagnoseFailureForExpr(Expr *expr);
 
   bool diagnoseAmbiguity(Expr *expr, ArrayRef<Solution> solutions);
-  bool diagnoseAmbiguityWithFixes(Expr *expr, ArrayRef<Solution> solutions);
+  bool diagnoseAmbiguityWithFixes(ArrayRef<Solution> solutions);
 
   /// Give the deprecation warning for referring to a global function
   /// when there's a method from a conditional conformance in a smaller/closer