Change double to single quotes

Signed-off-by: Patrick Creighton <pcreighton429@gmail.com>

Author: patrick-5546

ament_clang_tidy/ament_clang_tidy/main.py

@@ -163,7 +163,7 @@ def is_unittest_source(package, file_path):
             return ('%s/test/' % package) in file_path
 
         def is_protobuf_source(file_name):
-            if(file_name.endswith(".pb.cc") or file_name.endswith(".pb.h")):
+            if(file_name.endswith('.pb.cc') or file_name.endswith('.pb.h')):
                 return True
             return False