Add example for broken-collections-callable (#6167)

Author: DudeNr33

doc/data/messages/b/broken-collections-callable/bad.py

@@ -0,0 +1,6 @@
+from collections.abc import Callable
+from typing import Optional
+
+
+def func() -> Optional[Callable[[int], None]]:  # [broken-collections-callable]
+    ...

doc/data/messages/b/broken-collections-callable/good.py

@@ -0,0 +1,5 @@
+from typing import Callable, Optional
+
+
+def func() -> Optional[Callable[[int], None]]:
+    ...

doc/data/messages/b/broken-collections-callable/pylintrc

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+[master]
+py-version=3.9
+load-plugins=pylint.extensions.typing

doc/data/messages/b/broken-collections-callable/related.rst

@@ -0,0 +1 @@
+- `bpo-42965 <https://bugs.python.org/issue42965>`_