[fix] delete trailing whitespace

Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>

searx/templates/simple/categories.html

@@ -10,7 +10,7 @@
     'science': 'school-outline',
     'files': 'file-tray-full-outline',
     'social media': 'people-outline',
-}  -%}  
+}  -%}
 <div id="categories" class="search_categories">{{- '' -}}
     <div id="categories_container">
         {%- for category in categories -%}