Revert an inadvertent change from r348020.

llvm-svn: 348026

Author: AaronBallman

clang/.gitignore

@@ -29,6 +29,8 @@ cscope.out
 #==============================================================================#
 # Directories to ignore (do not add trailing '/'s, they skip symlinks).
 #==============================================================================#
+# Clang extra user tools, which is tracked independently (clang-tools-extra).
+tools/extra
 # Sphinx build products
 docs/_build
 docs/analyzer/_build