Fix clang-tidy ignoring compile_commands.json

test/command_callback/test_clang_tidy_command_callback.vader

@@ -68,7 +68,6 @@ Execute(The build directory should be used for header files):
   \ ale#Escape('clang-tidy')
   \   . ' -checks=' . ale#Escape('*') . ' %s'
   \   . ' -p ' . ale#Escape('/foo/bar')
-  \   . ' -- -x c++'
 
   call ale#test#SetFilename('test.hpp')