Bug 1727995 - Disable websocket over h2, r=necko-reviewers,dragana

Differential Revision: https://phabricator.services.mozilla.com/D126322

modules/libpref/init/StaticPrefList.yaml

@@ -10899,7 +10899,7 @@
 
 - name: network.http.http2.websockets
   type: RelaxedAtomicBool
-  value: true
+  value: false
   mirror: always
 
 - name: network.http.http2.enable-hpack-dump

testing/web-platform/meta/websockets/__dir__.ini

@@ -1,2 +1,3 @@
 lsan-disabled: true
 leak-threshold: [default:102400, tab:51200]
+prefs: [network.http.http2.websockets:true]