Remove use of backdrop from create and edit checker dialog

Change-Id: I99a790f65edf5dcfb5dc2693205efa097656018f
diff --git a/gr-checks/gr-checkers-list.html b/gr-checks/gr-checkers-list.html
index 36e8f85..6c62e4d 100644
--- a/gr-checks/gr-checkers-list.html
+++ b/gr-checks/gr-checkers-list.html
@@ -121,7 +121,7 @@
       </template>
     </nav>
 
-    <gr-overlay id="createOverlay" with-backdrop>
+    <gr-overlay id="createOverlay">
       <gr-dialog
           id="createDialog"
           confirm-label="Create"
@@ -138,7 +138,7 @@
         </div>
       </gr-dialog>
     </gr-overlay>
-    <gr-overlay id="editOverlay" with-backdrop>
+    <gr-overlay id="editOverlay">
       <gr-dialog
           id="editDialog"
           confirm-label="Save"