Cleanup: declare __all__ for many scripts in tools/

tools/utils_doc/rna_manual_reference_updater.py

@@ -28,6 +28,10 @@ or added to the Blender UI  translation table.
 
 URL is the: url_manual_prefix + url_manual_mapping[#id]
 '''
+__all__ = (
+    "main",
+)
+
 
 import os
 import argparse