Support Ruby 3.3

[joevandyk]

The following limits to ruby versions < 3.3: https://github.com/briandunn/flatware/blob/b6fa580f87ada1390160c0696588eab33684ea39/flatware-rspec.gemspec#L24

Could not find compatible versions

Because flatware-rspec >= 2.0.0.rc1, < 2.0.0 depends on Ruby >= 2.6, < 3.1
  and flatware-rspec < 2.0.0.rc1 depends on Ruby ~> 2.1,
  flatware-rspec < 2.0.0 requires Ruby >= 2.1, < 3.1.
And because flatware-rspec >= 2.0.0, < 2.1.0 depends on Ruby >= 2.6, < 3.2,
  flatware-rspec < 2.1.0 requires Ruby >= 2.1, < 3.2.
So, because flatware-rspec >= 2.1.0 depends on Ruby >= 2.6, < 3.3
  and current Ruby version is = 3.3.0

[WaKeMaTTa]

Solved by #74