Add Ruby 3.4 to CI, fix warning for 3.4 and error for 3.5/HEAD (#54)

Co-authored-by: Herwin Weststrate <herwin@quarantainenet.nl>
Co-authored-by: Herwin <herwinw@users.noreply.github.com>

Author: herwinw

.github/workflows/test.yml

@@ -24,6 +24,7 @@ jobs:
           - "3.1"
           - "3.2"
           - "3.3"
+          - "3.4"
           - head
         include:
           - { os: windows , ruby: mingw }

test/test_webrick_server.rb

@@ -6,7 +6,6 @@
 require_relative 'webrick_testing'
 require "xmlrpc/server"
 require 'xmlrpc/client'
-require 'logger'
 
 module TestXMLRPC
 class Test_Webrick < Test::Unit::TestCase