Increase sendRawText() wait hack to 400ms

I know this adds another 200ms to page load times, but it prevents pages
with a lot of text not rendering their text. Obviously better to just
fix the original bug.

webext/src/dom/text_builder.js

@@ -37,7 +37,7 @@ export default class extends utils.mixins(CommonMixin, SerialiseMixin) {
     setTimeout(() => {
       this.buildFormattedText();
       this._sendRawText();
-    }, 200);
+    }, 400);
   }
 
   buildFormattedText() {