Refactor: Simplify boolean conditional return statements in lib/ARCMigrate

Patch by Richard Thomson! (+a couple of modifications to address comments)

Differential revision: http://reviews.llvm.org/D10009

llvm-svn: 252261
diff --git a/clang/lib/ARCMigrate/TransGCAttrs.cpp b/clang/lib/ARCMigrate/TransGCAttrs.cpp
index 10fce19..2ae6b78 100644
--- a/clang/lib/ARCMigrate/TransGCAttrs.cpp
+++ b/clang/lib/ARCMigrate/TransGCAttrs.cpp
@@ -152,9 +152,7 @@
         return ID->getImplementation() != nullptr;
       if (ObjCCategoryDecl *CD = dyn_cast<ObjCCategoryDecl>(ContD))
         return CD->getImplementation() != nullptr;
-      if (isa<ObjCImplDecl>(ContD))
-        return true;
-      return false;
+      return isa<ObjCImplDecl>(ContD);
     }
     return false;
   }