Remove 'using namespace llvm' from the USRFinder.h header

This should fix the modules build
(http://lab.llvm.org:8011/builders/clang-x86_64-linux-selfhost-modules-2/).

llvm-svn: 307905

clang/include/clang/Tooling/Refactoring/Rename/USRFinder.h

@@ -21,8 +21,6 @@
 #include <string>
 #include <vector>
 
-using namespace llvm;
-
 namespace clang {
 
 class ASTContext;