enhance: update clear icon and increase size

resources/css/common.css

@@ -842,14 +842,12 @@ i.ti {
 
 .heading-bg {
   border-radius: 50%;
-  width: 12px;
-  height: 12px;
+  width: 14px;
+  height: 14px;
 
   &.remove {
     @apply border flex items-center justify-center;
 
-    font-size: 11px;
-    box-sizing: border-box;
     border-color: var(--border-color);
   }
 }

src/main/frontend/components/content.cljs

@@ -167,7 +167,7 @@
             {:title    (t :remove-background)
              :on-click (fn [_e]
                          (editor-handler/remove-block-property! block-id "background-color"))}
-            [:div.heading-bg.remove (ui/icon "x")]]]]
+            [:div.heading-bg.remove "-"]]]]
          
          [:hr.menu-separator]