test/ruby/test_jit.rb: Print a hint at exit of the original process

Otherwise, the hint is printed whenever fork is called.

http://rubyci.s3.amazonaws.com/debian9/ruby-master/log/20211025T093004Z.log.html.gz
```
[20244/21156] TestThread#test_fork_while_lockedyou may want to add tests for following insns, when you have a chance: checkmatch
you may want to add tests for following insns, when you have a chance: checkmatch
you may want to add tests for following insns, when you have a chance: checkmatch
 = 0.19 s
```

0 files changed, 0 insertions, 0 deletions