emoji-settings: Fix value of aria-label attribute of search input.

This commit changes the value of aria-label attribute of search
input of emoji settings form to be "Filter emojis" instead of
"Filter linkifiers".

static/templates/settings/emoji_settings_admin.hbs

@@ -31,7 +31,7 @@
     </form>
 
     <input type="text" class="search" placeholder="{{t 'Filter emojis' }}"
-      aria-label="{{t 'Filter linkifiers' }}"/>
+      aria-label="{{t 'Filter emojis' }}"/>
     <div class="progressive-table-wrapper" data-simplebar>
         <table class="table table-condensed table-striped wrapped-table admin_emoji_table">
             <thead>