Use getPatternFunctionDecl() over getTemplateInstantiationPattern()

The latter version doesn't find the very original template pattern for a
transformed lambda, while getPatternFunctionDecl() finds what we want for
constraint instantiation.

Author: zyn0217

clang/lib/Sema/SemaLambda.cpp

@@ -2433,8 +2433,7 @@ bool Sema::addInstantiatedCapturesToScope(
   if (LambdaPattern->capture_size() && !LambdaClass->capture_size()) {
     for (FunctionScopeInfo *Scope : llvm::reverse(FunctionScopes)) {
       auto *LSI = dyn_cast<LambdaScopeInfo>(Scope);
-      if (!LSI ||
-          LSI->CallOperator->getTemplateInstantiationPattern() != PatternDecl)
+      if (!LSI || getPatternFunctionDecl(LSI->CallOperator) != PatternDecl)
         continue;
       InstantiatingScope = LSI;
       break;