docs/devel/qapi-code-gen: Fix missing ':' in tagged section docs

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-ID: <20240120095327.666239-2-armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>

docs/devel/qapi-code-gen.rst

@@ -989,8 +989,8 @@ this::
   # @feature: Description text
 
 A tagged section starts with one of the following words:
-"Note:"/"Notes:", "Since:", "Example"/"Examples", "Returns:", "TODO:".
-The section ends with the start of a new section.
+"Note:"/"Notes:", "Since:", "Example:"/"Examples:", "Returns:",
+"TODO:".  The section ends with the start of a new section.
 
 The second and subsequent lines of sections other than
 "Example"/"Examples" should be indented like this::