move to official hcaptcha react component

assets/sass/components/_syntax.scss

@@ -67,6 +67,14 @@ div.highlight {
       width: 1em;
       height: 1em;
     }
+
+    .octicon-check {
+      @include themes.themed(
+        (
+          color: "success",
+        )
+      );
+    }
   }
 }