drop more llvm:: prefixes on OwningPtr<>

More cleanup after r149798.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@150379 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/tools/libclang/ARCMigrate.cpp b/tools/libclang/ARCMigrate.cpp
index 39c7d84..58f8ba4 100644
--- a/tools/libclang/ARCMigrate.cpp
+++ b/tools/libclang/ARCMigrate.cpp
@@ -56,7 +56,7 @@
   }
 
   TextDiagnosticBuffer diagBuffer;
-  llvm::OwningPtr<Remap> remap(new Remap());
+  OwningPtr<Remap> remap(new Remap());
 
   bool err = arcmt::getFileRemappings(remap->Vec, migrate_dir_path,&diagBuffer);