UX: improves dates on reports export UI (#7971)

- show it's UTC
- allows future
- shows date in more human readable format

app/assets/javascripts/admin/templates/components/admin-report.hbs

@@ -130,9 +130,7 @@
             </span>
 
             <div class="input">
-              {{date-picker-past
-                value=startDate
-                defaultDate=startDate}}
+              {{date-input date=startDate onChange=(action "onChangeStartDate")}}
             </div>
           </div>
 
@@ -142,9 +140,7 @@
             </span>
 
             <div class="input">
-              {{date-picker-past
-                value=endDate
-                defaultDate=endDate}}
+              {{date-input date=endDate onChange=(action "onChangeEndDate")}}
             </div>
           </div>
         {{/if}}