Fix backslashes in AF_PIPE (python#88355)

The correct syntax for AF_PIPE addresses is `\\.\pipe\blahblah`, not `\.\pipe{blahblah}`, but the syntax markup messed up the backslashes.

Author: cousteaulecommandant

Doc/library/multiprocessing.rst

@@ -2618,9 +2618,9 @@ Address Formats
   filesystem.
 
 * An ``'AF_PIPE'`` address is a string of the form
-  :samp:`r'\\\\.\\pipe\\{PipeName}'`.  To use :func:`Client` to connect to a named
+  :samp:`r'\\\\\\.\\pipe\\\\{PipeName}'`.  To use :func:`Client` to connect to a named
   pipe on a remote computer called *ServerName* one should use an address of the
-  form :samp:`r'\\\\{ServerName}\\pipe\\{PipeName}'` instead.
+  form :samp:`r'\\\\\\{ServerName}\\pipe\\\\{PipeName}'` instead.
 
 Note that any string beginning with two backslashes is assumed by default to be
 an ``'AF_PIPE'`` address rather than an ``'AF_UNIX'`` address.