[return-arg-in-generator] Add a details.rst only as the message is no…

…t raised anymore

doc/data/messages/r/return-arg-in-generator/details.rst

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+This is a message that isn't going to be raised for python > 3.3. It was raised
+for code like::
+
+    def interrogate_until_you_find_jack(pirates):
+        for pirate in pirates:
+            if pirate == "Captain Jack Sparrow":
+                return "Arrr! We've found our captain!"
+            yield pirate
+
+Which is now valid and equivalent to the previously expected::
+
+    def interrogate_until_you_find_jack(pirates):
+        for pirate in pirates:
+            if pirate == "Captain Jack Sparrow":
+                raise StopIteration("Arrr! We've found our captain!")
+            yield pirate

doc/data/messages/r/return-arg-in-generator/related.rst

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+- `PEP380 <https://peps.python.org/pep-0380/>`_
+- `Stackoverflow explanation <https://stackoverflow.com/a/16780113/2519059>`_