update version switcher for 2.18 (#2090) (#2098)

(cherry picked from commit 4eea539)

Co-authored-by: Sandra McCann <samccann@redhat.com>

docs/docsite/rst/conf.py

@@ -240,15 +240,15 @@
     'current_version': version,
     'latest_version': (
         'devel' if tags.has('all') else
-        '2.17' if tags.has('core_lang') or tags.has('core') else
+        '2.18' if tags.has('core_lang') or tags.has('core') else
         '10' if tags.has('ansible')
         else '<UNKNOWN>'
     ),
     # list specifically out of order to make latest work
     'available_versions': (
         ('devel',) if tags.has('all') else
         ('2.15_ja', '2.14_ja', '2.13_ja',) if tags.has('core_lang') else
-        ('2.17', '2.16', '2.15', 'devel',) if tags.has('core') else
+        ('2.18', '2.17', '2.16', 'devel',) if tags.has('core') else
         ('latest', '9', '2.9', 'devel') if tags.has('ansible')
         else '<UNKNOWN>'
     ),