fix: tracking code—remove async

- using async and defer on script tags is considered an [antipattern](https://almanac.httparchive.org/en/2022/javascript#async-defer-module-and-nomodule) as the defer will be ignored. Defer is the prefered behaviour in most situations.

components/forms/TrackingCodeForm.js

@@ -26,7 +26,7 @@ export default function TrackingCodeForm({ values, onClose }) {
           rows={3}
           cols={60}
           spellCheck={false}
-          defaultValue={`<script async defer data-website-id="${values.websiteUuid}" src="${
+          defaultValue={`<script defer data-website-id="${values.websiteUuid}" src="${
             document.location.origin
           }${basePath}/${trackerScriptName ? `${trackerScriptName}.js` : 'umami.js'}"></script>`}
           readOnly