Support Ruby 3.4's `it` keyword

[amomchilov]

... once upstream Sorbet starts supporting it. sorbet#8375

#228 configured Prism to parse in Ruby 3.3 mode:

sorbet/parser/prism/Parser.h

Lines 19 to 20 in 082c0c9

	// The version of Ruby syntax that we're parsing with Prism. This determines what syntax is supported or not.
	static constexpr std::string_view ParsedRubyVersion = "3.3.0";

We'll need to update that to 3.4 (reference), then update the translation layer to match Sorbet.

[Tripple-A]

@amomchilov, we ran into this issue today with the unavailable support for “it” and in the process of doing some findings, I found this issue you created and your previous work on translating the “it” keyword.

From your PR, I saw that Prism already parses it as PM_IT_LOCAL_VARIABLE_READ_NODE, and the translation layer currently marks it as unreachable.

If the only missing piece is translating that node to _1 and updating the parser to 3.4 mode, I’d be happy to take a stab at it and open a PR. Is there anything else (e.g. broader Ruby 3.4 compatibility, other blockers to moving this upstream) that I should be aware of before doing so?