[clang-tidy] update links to Google Code Style in docs

Summary: Because of the recent Google Code shutdown links to the Google Code Style up there are no longer relevant.

Reviewers: alexfh, hokein

Subscribers: cfe-commits

Patch by Kirill Bobyrev!

Differential Revision: http://reviews.llvm.org/D17602

llvm-svn: 261868
diff --git a/clang-tools-extra/clang-tidy/google/UsingNamespaceDirectiveCheck.h b/clang-tools-extra/clang-tidy/google/UsingNamespaceDirectiveCheck.h
index b88a2d3..a36f380 100644
--- a/clang-tools-extra/clang-tidy/google/UsingNamespaceDirectiveCheck.h
+++ b/clang-tools-extra/clang-tidy/google/UsingNamespaceDirectiveCheck.h
@@ -19,7 +19,7 @@
 
 /// Finds using namespace directives.
 ///
-/// http://google-styleguide.googlecode.com/svn/trunk/cppguide.xml?showone=Namespaces#Namespaces
+/// https://google.github.io/styleguide/cppguide.html#Namespaces
 ///
 /// The check implements the following rule of the Google C++ Style Guide:
 ///