Range#step with no block and non-Numeric values gives undefined method `step'

[eregon]

$ ruby -e 'p ("a".."z").step(3).to_a'   
["a", "d", "g", "j", "m", "p", "s", "v", "y"]
$ jt -q ruby -e 'p ("a".."z").step(3).to_a'
<internal:core> core/enumerator.rb:103:in `each_with_block': undefined method `step' for Truffle::RangeOperations:Module (NoMethodError)
	from <internal:core> core/enumerator.rb:94:in `each'
	from <internal:core> core/enumerable.rb:291:in `to_a'
	from -e:1:in `<main>'

Found with @nirvdrum

Trivial to fix, I'll fix it.