Drop Ruby 2.3 and 2.4 support as up-to-date sniffer works only in 2.5

Ruby 2.3 and 2.4 have already reached their end of life

.rubocop.yml

@@ -1,8 +1,3 @@
 Style/Documentation:
   Exclude:
     - 'example/**/*'
-
-# Rubocop does not support TargetRubyVersion 2.3, while required_ruby_version
-# in the gemspec is set to 2.3.0. This will prevent related offense.
-Gemspec/RequiredRubyVersion:
-  Enabled: false

yabeda-http_requests.gemspec

@@ -12,7 +12,7 @@ Gem::Specification.new do |spec|
   spec.description   = 'Extends Yabeda metrics to collect external calls'
   spec.homepage      = 'https://github.com/yabeda-rb/yabeda-http_requests'
   spec.license       = 'MIT'
-  spec.required_ruby_version = Gem::Requirement.new('>= 2.3.0')
+  spec.required_ruby_version = Gem::Requirement.new('>= 2.5')
 
   spec.metadata['homepage_uri'] = spec.homepage
   spec.metadata['source_code_uri'] = 'https://github.com/yabeda-rb/yabeda-http_requests'