Update Vendored MQuickJS

[probably-not]

This updates the vendored MQuickJS code to the latest version (commit sha ee50431eac9b14b99f722b537ec4cac0c8dd75ab).

Since the initial vendoring of the code, there have been several fixes including various fixes to things related to memory bugs. In some experimentation, I was hitting sporadic crashes that look like this:

beam.smp(96296,0x16eecb000) malloc: Incorrect checksum for freed object 0x125822800: probably modified after being freed.
Corrupt value: 0x125820591
beam.smp(96296,0x16eecb000) malloc: *** set a breakpoint in malloc_error_break to debug
[os_mon] cpu supervisor port (cpu_sup): Erlang has closed
[os_mon] memory supervisor port (memsup): Erlang has closed

After updating the vendored code, I have yet to hit these crashes.