DEV: Use isSecureContext for service worker registrations (#19407)

Currently, we check if the site is loaded over `https` before
registering the service worker. This prevents the service worker from
being registered in a standard dev/test setup.

This change replaces the protocol check with `isSecureContext`
property check.

In addition to resources delivered over `https`, `isSecureContext`
returns `true` for resources loaded over `http://127.0.0.1`, `http://localhost`,
`http://*.localhost` and `file://`.

app/assets/javascripts/discourse/app/lib/register-service-worker.js

@@ -5,9 +5,7 @@ export function registerServiceWorker(
   serviceWorkerURL,
   registerOptions = {}
 ) {
-  const isSecured = document.location.protocol === "https:";
-
-  if (isSecured && "serviceWorker" in navigator) {
+  if (window.isSecureContext && "serviceWorker" in navigator) {
     const caps = container.lookup("capabilities:main");
     const isAppleBrowser =
       caps.isSafari ||