Bug 1748544 - enable browser_autoplay_policy_webRTC_permission.js. r=media-playback-reviewers,padenot

This test looks good on current mc [1], we should re-enable it.

[1] https://treeherder.mozilla.org/jobs?repo=try&revision=97528a5285862103bcecc6fd3bd3e47f1c3df099

Differential Revision: https://phabricator.services.mozilla.com/D135088

dom/media/autoplay/test/browser/browser.ini

@@ -21,5 +21,4 @@ https_first_disabled = true
 [browser_autoplay_policy_web_audio.js]
 [browser_autoplay_policy_web_audio_with_gum.js]
 [browser_autoplay_policy_webRTC_permission.js]
-skip-if = true # Bug 1518429
 [browser_autoplay_videoDocument.js]