[IMP] doc: specify the API examples are in python2

Odoo 11 is python 3 but the xmlrpc interface works with python 2 too.
The example should probably be migrated to use python 3.
In the meantime specify exactly these examples are python 2 to avoid the
confusion.

Fixes #24232

doc/_extensions/odoo_ext/switcher.py

@@ -1,7 +1,8 @@
 from docutils import nodes, utils
 from docutils.parsers.rst import Directive
 
-from pygments.lexers import get_lexer_by_name
+from pygments.lexers import get_lexer_by_name, PythonLexer
+PythonLexer.name = 'Python 2'
 
 def setup(app):
     app.add_directive('switcher', SwitcherDirective)