[AST] Remove ASTContext from getThisType (NFC)

Summary:
https://reviews.llvm.org/D54862 removed the usages of `ASTContext&` from
within the `CXXMethodDecl::getThisType` method. Remove the parameter
altogether, as well as all usages of it. This does not result in any
functional change because the parameter was unused since
https://reviews.llvm.org/D54862.

Test Plan: check-clang

Reviewers: akyrtzi, mikael

Reviewed By: mikael

Subscribers: mehdi_amini, dexonsmith, cfe-commits

Differential Revision: https://reviews.llvm.org/D56509

llvm-svn: 350914
diff --git a/clang/lib/Sema/SemaDeclAttr.cpp b/clang/lib/Sema/SemaDeclAttr.cpp
index b5859d1..241eea4 100644
--- a/clang/lib/Sema/SemaDeclAttr.cpp
+++ b/clang/lib/Sema/SemaDeclAttr.cpp
@@ -1151,8 +1151,7 @@
 
 static bool checkForConsumableClass(Sema &S, const CXXMethodDecl *MD,
                                     const ParsedAttr &AL) {
-  ASTContext &CurrContext = S.getASTContext();
-  QualType ThisType = MD->getThisType(CurrContext)->getPointeeType();
+  QualType ThisType = MD->getThisType()->getPointeeType();
 
   if (const CXXRecordDecl *RD = ThisType->getAsCXXRecordDecl()) {
     if (!RD->hasAttr<ConsumableAttr>()) {
@@ -1265,7 +1264,7 @@
   //
   //} else if (const CXXConstructorDecl *Constructor =
   //             dyn_cast<CXXConstructorDecl>(D)) {
-  //  ReturnType = Constructor->getThisType(S.getASTContext())->getPointeeType();
+  //  ReturnType = Constructor->getThisType()->getPointeeType();
   //
   //} else {
   //