[prism] False positive for `EmptyLineAfterGuardClause` for heredoc

[Andy Waite]

With the parser set to prism, the following causes a false positive:

def foo
  raise(<<~MSG) unless 1 == 2
    a
    b
  MSG

  true
end

% bin/rubocop . -V                                                                                                                                               andyw8
1.63.2 (using Prism 0.26.0, rubocop-ast 1.31.2, running on ruby 3.3.0) [x86_64-linux]
  - rubocop-graphql 1.5.1
  - rubocop-minitest 0.35.0
  - rubocop-performance 1.21.0
  - rubocop-rails 2.24.1
  - rubocop-sorbet 0.8.1