This reverts commit aae8014.

This workaround was added after the update to Gecko 121. The issues
with first contentful paint are not here anymore so we can remove
it and avoid synthesizing FCP events at the wrong time which were
causing issues when taking screenshots of the web contents.

When those generated FCPs were issued, the Gecko compositor was
not in a ready state to generate a screenshot and thus an exception
was generated. Gecko was not handling it properly so it was
affecting subsequent JNI calls causing crashes and hangs in Gecko.

Fixes #1638

The FCP event is not emitted by GeckoView if the page is loaded from the cache
(either HTTP or back/forward). As a result many things are not properly set up
in Wolvic, like the current active session, resulting in many cases in web
contents not visible on app start.

In those cases we should generate and emit it to get things working.