Bug 1677521 - Enable test_trr.js::test25e r=necko-reviewers,kershaw

This test was disabled in Bug 1666072 when we set the allowSTS=false for
captive portal requests to prevent a HSTS upgrade redirect.

Bug 1681683 added a different property (isOCSP) to be able to differentiate
OCSP channels from regular ones, so even if captive portal channels have
allowSTS=false, they still use the same TRR mode as was initially set
on the channel. This means the test will now work in mode3 as well.

Differential Revision: https://phabricator.services.mozilla.com/D106892

netwerk/test/unit/test_trr.js

@@ -1088,7 +1088,7 @@ add_task(async function test25d() {
 });
 
 // TRR-only check that captivedetect.canonicalURL is resolved via native DNS
-add_task({ skip_if: () => true }, async function test25e() {
+add_task(async function test25e() {
   dns.clearCache(true);
   Services.prefs.setIntPref("network.trr.mode", 3); // TRR-only
   Services.prefs.setCharPref(