fix: Override FAB styling (#11752)

Author: ryanahamilton

airflow/www/static/css/main.css

@@ -432,3 +432,9 @@ label[for="timezone-other"],
   top: 2px;
   border: 0;
 }
+
+/* Overrides undesireable styling rendered by FAB markup */
+.dropdown-menu .filter.btn {
+  border: 0;
+  border-radius: 0;
+}