[fix 3/3] actually only hide them for tabs

The categories.html template is used in three places:

1) for the tabs on the result page
2) for the default category selection in the preferences
3) for the advanced search category selection in the oscar theme

The search_on_category_select plugin only makes the checkboxes in 1)
behave like tabs. The previous commit however hides the checkboxes
in all three places when the plugin is loaded, which we don't want:
The categories in 2) and 3) always act like checkboxes, so the
checkboxes in these places should actually always be visible.

searx/static/plugins/css/search_on_category_select.css

@@ -1 +1 @@
-.category input { display: none; }
+.search-tabs .category input { display: none; }