This PR fixes token incompatibility for `Prism::Translation::Parser::Lexer` when using backquoted heredoc indetiner:

```ruby
<<-`  FOO`
a
b
     FOO
```

## Parser gem (Expected)

Returns `tXSTRING_BEG` as the first token:

```console
$ bundle exec ruby -Ilib -rparser/ruby33 -ve \
'buf = Parser::Source::Buffer.new("example.rb"); buf.source = File.read("example.rb"); p Parser::Ruby33.new.tokenize(buf)'
ruby 3.3.0 (2023-12-25 revision https://github.com/ruby/prism/commit/5124f9ac75) [x86_64-darwin22]
[s(:xstr,
  s(:str, "a\n"),
  s(:str, "b\n")), [], [[:tXSTRING_BEG, ["<<`", #<Parser::Source::Range example.rb 0...10>]],
[:tSTRING_CONTENT, ["a\n", #<Parser::Source::Range example.rb 11...13>]],
[:tSTRING_CONTENT, ["b\n", #<Parser::Source::Range example.rb 13...15>]],
[:tSTRING_END, ["  FOO", #<Parser::Source::Range example.rb 15...23>]], [:tNL, [nil, #<Parser::Source::Range example.rb 10...11>]]]]
```

## `Prism::Translation::Parser` (Actual)

Previously, the tokens returned by the Parser gem were different. The escaped backslash does not match in the `tSTRING_BEG` token and
value of `tSTRING_END` token.

```console
$ bundle exec ruby -Ilib -rprism -rprism/translation/parser33 -ve \
'buf = Parser::Source::Buffer.new("example.rb"); buf.source = File.read("example.rb"); p Prism::Translation::Parser33.new.tokenize(buf)'
ruby 3.3.0 (2023-12-25 revision https://github.com/ruby/prism/commit/5124f9ac75) [x86_64-darwin22]
[s(:xstr,
  s(:str, "a\n"),
  s(:str, "b\n")), [], [[:tSTRING_BEG, ["<<\"", #<Parser::Source::Range example.rb 0...10>]],
[:tSTRING_CONTENT, ["a\n", #<Parser::Source::Range example.rb 11...13>]],
[:tSTRING_CONTENT, ["b\n", #<Parser::Source::Range example.rb 13...15>]],
[:tSTRING_END, ["`  FOO`", #<Parser::Source::Range example.rb 15...23>]], [:tNL, [nil, #<Parser::Source::Range example.rb 10...11>]]]]
```

After this correction, the AST and tokens returned by the Parser gem are the same:

```console
$ bunlde exec ruby -Ilib -rprism -rprism/translation/parser33 -ve \
'buf = Parser::Source::Buffer.new("example.rb"); buf.source = File.read("example.rb"); p Prism::Translation::Parser33.new.tokenize(buf)'
ruby 3.3.0 (2023-12-25 revision https://github.com/ruby/prism/commit/5124f9ac75) [x86_64-darwin22]
[s(:xstr,
  s(:str, "a\n"),
  s(:str, "b\n")), [], [[:tXSTRING_BEG, ["<<`", #<Parser::Source::Range example.rb 0...10>]],
[:tSTRING_CONTENT, ["a\n", #<Parser::Source::Range example.rb 11...13>]],
[:tSTRING_CONTENT, ["b\n", #<Parser::Source::Range example.rb 13...15>]],
[:tSTRING_END, ["  FOO", #<Parser::Source::Range example.rb 15...23>]], [:tNL, [nil, #<Parser::Source::Range example.rb 10...11>]]]]
```

https://github.com/ruby/prism/commit/308f8d85a1