Issue #26462: Doc: reduce literal_block warnings, fix syntax highlighting.

Patch by Julien Palard.
diff --git a/Doc/library/socketserver.rst b/Doc/library/socketserver.rst
index 98d2c46..087f4e0 100644
--- a/Doc/library/socketserver.rst
+++ b/Doc/library/socketserver.rst
@@ -479,7 +479,9 @@
 
 The output of the example should look something like this:
 
-Server::
+Server:
+
+.. code-block:: shell-session
 
    $ python TCPServer.py
    127.0.0.1 wrote:
@@ -487,7 +489,9 @@
    127.0.0.1 wrote:
    b'python is nice'
 
-Client::
+Client:
+
+.. code-block:: shell-session
 
    $ python TCPClient.py hello world with TCP
    Sent:     hello world with TCP
@@ -599,7 +603,9 @@
        server.server_close()
 
 
-The output of the example should look something like this::
+The output of the example should look something like this:
+
+.. code-block:: shell-session
 
    $ python ThreadedTCPServer.py
    Server loop running in thread: Thread-1