CSS: Don't set max-width for fullscreen Converse in smaller viewports

sass/_chatbox.scss

@@ -510,7 +510,6 @@
         border: var(--flyout-padding) solid var(--chat-head-color);
         bottom: 0;
     }
-
     .chat-head {
         height: var(--fullpage-chat-head-height);
         padding: 0;
@@ -526,9 +525,17 @@
             @include make-col(2);
         }
     }
-
     .chatbox {
         margin: 0;
+        .box-flyout {
+            box-shadow: none;
+            overflow: hidden;
+        }
+    }
+}
+
+#conversejs.converse-embedded {
+    .chatbox {
         @include make-col-ready();
         @include media-breakpoint-up(md) {
             @include make-col(8);
@@ -539,11 +546,6 @@
         @include media-breakpoint-up(xl) {
             @include make-col(10);
         }
-
-        .box-flyout {
-            box-shadow: none;
-            overflow: hidden;
-        }
     }
 }