[fix] Removes `/>` ending tags for void HTML elements

Removes ``/>`` ending tags for void elements [1] and replaces them with ``>``.
Part of the larger cleanup to cleanup invalid HTML throughout the codebase [2].

[1] https://html.spec.whatwg.org/multipage/syntax.html#void-elements
[2] https://github.com/searxng/searxng/issues/3793

searx/templates/simple/elements/infobox.html

@@ -38,7 +38,7 @@
               <input type="hidden" name="safesearch" value="{{ safesearch }}">
               <input type="hidden" name="theme" value="{{ theme }}">
               {%- if timeout_limit -%}<input type="hidden" name="timeout_limit" value="{{ timeout_limit|e }}" >{%- endif -%}
-              <input type="submit" value="{{ suggestion }}" />
+              <input type="submit" value="{{ suggestion }}">
             </form>
           {%- endfor -%}
         </div>