Add rule to handle missing docs for a new module (#6008)

Mitigates #5975

A better (but more involved) fix will be to update the AI part of log
classifier to better notice that this line was the real failure

aws/lambda/log-classifier/ruleset.toml

@@ -308,3 +308,7 @@ pattern = '^Mergeability Error: .*'
 [[rule]]
 name = 'GHA error'
 pattern = '^##\[error\](.*)'
+
+[[rule]]
+name = 'New modules are not documented correctly'
+pattern = 'You added the following module\(s\) to the PyTorch namespace .* but they'