fud: --to vcd_json flag leads to stack overflor

[eys29]

fud e examples/futil/multi-component.futil --to vcd_json --through icarus-verilog

led to error:

[[fud] ERROR: `vcdump --pretty' failed:
=====STDERR=====
Error: 
thread 'main' has overflowed its stack
fatal runtime error: stack overflow
=====STDOUT=====

[sampsyo]

I think we can probably close this as of #1891? This seems to have been the only place where we used fud's vcd_json state in the docs, and it's likely that something has simply changed w/r/t the size tolerances in vcdump.