Drop support for ruby 2.3

Rakefile

@@ -121,7 +121,7 @@ task 'gem:native' do
   verbose = ENV['V'] || '0'
 
   grpc_config = ENV['GRPC_CONFIG'] || 'opt'
-  ruby_cc_versions = ['3.0.0', '2.7.0', '2.6.0', '2.5.0', '2.4.0', '2.3.0'].join(':')
+  ruby_cc_versions = ['3.0.0', '2.7.0', '2.6.0', '2.5.0', '2.4.0'].join(':')
 
   if RUBY_PLATFORM =~ /darwin/
     FileUtils.touch 'grpc_c.32.ruby'

grpc.gemspec

@@ -13,7 +13,7 @@ Gem::Specification.new do |s|
   s.description   = 'Send RPCs from Ruby using GRPC'
   s.license       = 'Apache-2.0'
 
-  s.required_ruby_version = '>= 2.3.0'
+  s.required_ruby_version = '>= 2.4.0'
 
   s.files = %w( Makefile .yardopts )
   s.files += %w( etc/roots.pem )

tools/run_tests/artifacts/distribtest_targets.py

@@ -361,7 +361,6 @@ def targets():
         PythonDistribTest('linux', 'x64', 'ubuntu1604', source=True),
         PythonDistribTest('linux', 'x64', 'ubuntu1804', source=True),
         # Ruby
-        RubyDistribTest('linux', 'x64', 'jessie', ruby_version='ruby_2_3'),
         RubyDistribTest('linux', 'x64', 'jessie', ruby_version='ruby_2_4'),
         RubyDistribTest('linux', 'x64', 'jessie', ruby_version='ruby_2_5'),
         RubyDistribTest('linux', 'x64', 'jessie', ruby_version='ruby_2_6'),
@@ -370,7 +369,7 @@ def targets():
         RubyDistribTest('linux',
                         'x64',
                         'jessie',
-                        ruby_version='ruby_2_3',
+                        ruby_version='ruby_2_4',
                         source=True),
         RubyDistribTest('linux', 'x64', 'centos7'),
         RubyDistribTest('linux', 'x64', 'fedora23'),