Fix EnvUtil.invoke_ruby on Ruby < 3.3

[rhenium]

Only pass --parser= option to Ruby versions that accept it. test-unit-ruby-core currently supports Ruby >= 2.3.

---

With v1.0.8 assertion methods that spawn child process are broken. For example, https://github.com/ruby/openssl/actions/runs/18215689022/job/51864356336 failed with:

[...]
10) Failure: test_unloaded_openssl_provider(OpenSSL::TestProvider):
  assert_separately failed with error message
  pid 2438 exit 1
  | /opt/hostedtoolcache/Ruby/3.2.9/x64/bin/ruby: invalid option --parser=parse.y  (-h will show valid options) (RuntimeError)
[...]

[rhenium]

Superseded by #15