remove dark mode by default as 7.2 has shimmer issue

_config.yml

@@ -88,7 +88,7 @@ pageviews:
 #     light — Use the light color scheme
 #     dark — Use the dark color scheme
 #
-theme_mode: dark # [light | dark]
+theme_mode: # [light | dark]
 
 # The CDN endpoint for media resources.
 # Notice that once it is assigned, the CDN url