Drop 500MB cap for 9.1

[headius]

We need to do this in the native launchers as well, but I'm not sure if we need to do it in jruby-launcher if we do it in mjruby.

This is a placeholder issue while we decide.

Relates to jruby/jruby#3739.

[headius]

Done except for rebuilding .exe and releasing gem. I believe @enebo will look at building .exe.

[headius]

See aaea124.