fix(default-flatpaks): remove check for fedora-third-party opt-out

[ibaidev]

This change simplifies Fedora third-party repository opt-out in system-flatpak-setup by removing the call to /usr/lib/fedora-third-party/fedora-third-party-opt-out and using /usr/bin/fedora-third-party disable when available.

The opt-out helper is single-purpose: it flips the third-party status from unset to disabled and exists to allow a different pkexec configuration so an admin can opt out without authenticating on first run. This seems the best option if we bootc switch from a fresh install, but if the third-party status has already been set, any call to this helper prints a message directing callers to /usr/bin/fedora-third-party disable and returns a non-zero exit code, which causes our setup flow to abort before the intended disable step can run.

There may be a more sophisticated way to solve this, but relying directly on /usr/bin/fedora-third-party disable removes the redundant helper invocation, avoids the premature failure path, and ensures the disable action executes consistently on both first and subsequent runs.

[xynydev]

The reasoning sounds solid here. Hope this is the case, as I'm approving the change :p

Sorry it took so long

[Copilot]

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[xynydev]

Why the f-- did copilot try to review this?