Ruby >= 4.1.0 allows trailing comma in method signature

[eikes]

See "Allow trailing comma in method signature":

https://bugs.ruby-lang.org/issues/19107
ruby/prism#3920

So this is now valid ruby:

def f(a,)

The colorize special code test is no longer passing because of this change in latest Prism: https://github.com/ruby/irb/actions/runs/22390686601/job/64811636988

This PR fixes the failing test with latest Prism here by removing this special case from the color test.

I noticed this failure in the following PR, which will pass after merging this PR: #1177

[eikes]

Alternatively the Prism version could be inspected and the test adapted:

    def test_colorize_trailing_comma_in_method_definition_complete_false
      prism_1_9_1_or_later = ENV['PRISM_VERSION'] == 'latest' || Gem::Version.new(Prism::VERSION) >= Gem::Version.new('1.9.1')
      
      code = "def f(a,)" 

      result = if prism_1_9_1_or_later 
        "#{GREEN}def#{CLEAR} #{BLUE}#{BOLD}f#{CLEAR}(a,)" 
      else
        "#{GREEN}def#{CLEAR} #{BLUE}#{BOLD}f#{CLEAR}(a#{RED}#{REVERSE},#{CLEAR})"
      end

      assert_equal_with_term(result, code, complete: false)

      assert_equal_with_term(code, code, complete: false, tty: false)

      assert_equal_with_term(code, code, complete: false, colorable: false)

      assert_equal_with_term(result, code, complete: false, tty: false, colorable: true)
    end