Documentation/sphinx: fix Python string escapes

Documentation/sphinx: fix Python string escapes

commit 86a0adc029d338f0da8989e7bb453c1114d51960 upstream.

Python 3.6 introduced a DeprecationWarning for invalid escape sequences.
This is upgraded to a SyntaxWarning in Python 3.12, and will eventually
be a syntax error.

Fix these now to get ahead of it before it's an error.

Signed-off-by: Benjamin Gray <bgray@linux.ibm.com>
Message-ID: <20230912060801.95533-3-bgray@linux.ibm.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Cc: Justin Forbes <jforbes@fedoraproject.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>