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

Patch by Julien Palard.
diff --git a/Doc/library/cgi.rst b/Doc/library/cgi.rst
index da15e00..1bfdb39 100644
--- a/Doc/library/cgi.rst
+++ b/Doc/library/cgi.rst
@@ -450,7 +450,9 @@
 invoked as a script, the file will dump its environment and the contents of the
 form in HTML form. Give it the right mode etc, and send it a request.  If it's
 installed in the standard :file:`cgi-bin` directory, it should be possible to
-send it a request by entering a URL into your browser of the form::
+send it a request by entering a URL into your browser of the form:
+
+.. code-block:: none
 
    http://yourhostname/cgi-bin/cgi.py?name=Joe+Blow&addr=At+Home
 
@@ -542,4 +544,3 @@
    field values should be supplied in, but knowing whether a request was
    received from a conforming browser, or even from a browser at all, is tedious
    and error-prone.
-