QtWebView loadHtml will show html source (not rendered page) on Android 4.3

When running QtWebView on android 4.3 (api level < 19, not chromium based), loadHtml call will show the html source, not the rendered page.

It is the same issue as:

https://stackoverflow.com/questions/30420949/webview-shows-source-html-with-loaddatawithbaseurl-not-rendered-view

Change the mime type from "text/html;charset=UTF-8" to simple "text/html" fix the issue.

It only happens to Android 4.3 (maybe also earlier versions too), more recent version of Android does not have this issue. (tested on 5.x and 6.x)