Update ArgumentError message for Ractor.select

Author: jhawthorn

bootstraptest/test_ractor.rb

@@ -316,7 +316,7 @@ def test n
 } unless (ENV.key?('TRAVIS') && ENV['TRAVIS_CPU_ARCH'] == 'arm64') # https://bugs.ruby-lang.org/issues/17878
 
 # Exception for empty select
-assert_match /specify at least one ractor/, %q{
+assert_match /specify at least one Ractor::Port or Ractor/, %q{
   begin
     Ractor.select
   rescue ArgumentError => e

ractor.rb

@@ -267,7 +267,7 @@ def self.count
   #
   # TBD
   def self.select(*ports)
-    raise ArgumentError, 'specify at least one ractor or `yield_value`' if ports.empty?
+    raise ArgumentError, 'specify at least one Ractor::Port or Ractor' if ports.empty?
 
     monitors = {} # Ractor::Port => Ractor