Tests: fix incorrect check for hidden dir

Copy-pasted mistake in tests and tools.

tests/check_deprecated.py

@@ -53,10 +53,8 @@ def is_source_any(filename):
 
 def source_list(path, filename_check=None):
     for dirpath, dirnames, filenames in os.walk(path):
-
-        # skip '.svn'
-        if dirpath.startswith("."):
-            continue
+        # skip '.git'
+        dirnames[:] = [d for d in dirnames if not d.startswith(".")]
 
         for filename in filenames:
             if filename_check is None or filename_check(filename):