Fix downloading libraries for Forge 1.7.2

[aecsocket]

In our library download code path we have a fallback way of creating a URL if we don't have a library URL in the game version metadata, introduced in #4494:

// We lack an artifact URL, so fall back to constructing one ourselves.
// PrismLauncher just ignores the library if this is the case, so it's
// probably not needed, but previous code revisions of the Modrinth App
// intended to do this, so we keep that behavior for compatibility.

Even though the library is "probably not needed", we will still fatally abort if we can't download it. However, the URL is not guaranteed to even point to a real download since we're pulling it out of thin air, so this should be silently ignored (with a log message).

Also bumped up recursion limit because somehow this tiny change was enough to tip rustc over the edge with calculating Send/Sync bounds.