gh-102873: logging.LogRecord docs: improve description of msg parameter (GH-102875)

(cherry picked from commit f2e5a6e)

Co-authored-by: Amin Alaee <mohammadamin.alaee@gmail.com>
Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>

Author: 3 people

Diff for: Doc/library/logging.rst

@@ -796,8 +796,9 @@ wire).
    :type lineno: int
 
    :param msg: The event description message,
-      which can be a %-format string with placeholders for variable data.
-   :type msg: str
+      which can be a %-format string with placeholders for variable data,
+      or an arbitrary object (see :ref:`arbitrary-object-messages`).
+   :type msg: typing.Any
 
    :param args: Variable data to merge into the *msg* argument
       to obtain the event description.