Enable syntax highlighting in tests

[rohitpaulk]

In the test environment, we have syntax highlighting disabled:

frontend/app/lib/highlighter-cache.js

Line 17 in e2aab06

if (config.environment === 'test' || !window.fetch || !window.XMLHttpRequest) {

. This is because pretender seems to interfere with wasm requests and return invalid contents back. Can we see if there's a way to enable this and bypass pretender?

[rohitpaulk]

We actually ended up with a failure here, went unnoticed for days - @VasylMarchuk let's prioritize this once you're done with the ember 5 stuff and findRecord research

[rohitpaulk]

@VasylMarchuk actually, let's ignore this and do #1231 instead