Fix RubyLex's heredoc_with_hembexpr test to avoid ripper tokenizing i…

[tompng]

Fix test_heredoc_with_embexpr because the expected result was wrong.
We also have to avoid ripper's bug https://bugs.ruby-lang.org/issues/19563 in test cases because I want this test to be executed in all supported ruby version.

require 'ripper'
code = [
  %q(<<A+%W[#{<<B),
  %q(#{<<C+%W[),
  %q(a),
  %q(C),
  %q(a), # if this line is an empty string `%(),` then `Ripper.tokenize(code).join == code` returns false
  %q(]}),
  %q(}),
  %q(A),
  %q(B),
  %q(}),
  %q(]),
  %q()
].join("\n")
puts RUBY_VERSION
p Ripper.tokenize(code).join == code #=> true in ruby 2.7~3.2