[UG] Fix typo causing Sphinx warning "Inconsistent block quoting"

Author: LittleJ

user_guide_src/source/incoming/filters.rst

@@ -168,8 +168,6 @@ would apply to every AJAX request.
 
 .. note:: The AJAX requests depends on the ``X-Requested-With`` header, which in some cases is not sent by default in XHR requests via JavaScript (i.e. fetch). See the :doc:`AJAX Requests </general/ajax>` section on how to avoid this problem.
 
-::
-
 $filters
 ========