MDL-70829 tool_lp: Add empty alt text for decorative image

* The decorative image for the course modules in the user competency
summary modal is missing an empty alt text.

admin/tool/lp/templates/user_competency_summary_in_course.mustache

@@ -49,7 +49,7 @@
         <p>
         <ul class="inline list-inline">
         {{#coursemodules}}
-            <li class="list-inline-item"><a href="{{url}}"><img class="icon" src="{{iconurl}}"> {{name}} </a></li>
+            <li class="list-inline-item"><a href="{{url}}"><img class="icon" src="{{iconurl}}" alt=""> {{name}} </a></li>
         {{/coursemodules}}
         {{^coursemodules}}
             <li class="list-inline-item"><span class="alert">{{#str}}noactivities, tool_lp{{/str}}</span></li>