Bug: Fix missing close button on mobile chat window (#600)

Co-authored-by: Pranav Raj Sreepuram <pranavrajs@gmail.com>

app/javascript/widget/components/ChatHeader.vue

@@ -3,7 +3,7 @@
     <h2 class="title">
       {{ title }}
     </h2>
-    <span class="close" @click="closeWindow"></span>
+    <span class="close-button" @click="closeWindow"></span>
   </header>
 </template>
 
@@ -54,27 +54,8 @@ export default {
     color: $color-heading;
   }
 
-  .close {
-    cursor: pointer;
-    position: relative;
-    width: $space-two;
-
-    &:before,
-    &:after {
-      position: absolute;
-      left: $space-small;
-      top: $space-smaller;
-      content: ' ';
-      height: $space-normal;
-      width: 2px;
-      background-color: $color-heading;
-    }
-    &:before {
-      transform: rotate(45deg);
-    }
-    &:after {
-      transform: rotate(-45deg);
-    }
+  .close-button {
+    display: none;
   }
 }
 </style>