Issue #15103: remove the NUL character (serving as a Mercurial binary marker)…

Issue #15103: remove the NUL character (serving as a Mercurial binary marker) from Python/importlib.h.
Instead the email notification hook uses a configuration option to omit importlib.h diffs.

Python/freeze_importlib.py

@@ -24,7 +24,6 @@ def main(input_path, output_path):
     lines.append('};\n')
     with open(output_path, 'w', encoding='utf-8') as output_file:
         output_file.write('\n'.join(lines))
-        output_file.write('/* Mercurial binary marker: \x00 */')
         # Avoid a compiler warning for lack of EOL
         output_file.write('\n')