ZJIT: Don't disable GC during profiling

[tekknolagi]

This is unnecessarily expensive and we don't allocate on the Ruby heap at all during profiling. If we want, we can try to do something like disabling allocation so we get an assertion failure

[tekknolagi]

This happens in with_vm_lock

[tekknolagi]

@alanwu-shopify-inc will continue by using Sync.