Centralize Ruby Version to .ruby-version

Set minimum version of Rubocop to 1.61
This is to support `.ruby-version`: rubocop/rubocop#12645

.github/workflows/benchmark.yml

@@ -13,7 +13,6 @@ jobs:
     - name: Set up Ruby
       uses: ruby/setup-ruby@v1
       with:
-        ruby-version: 3.1
         bundler-cache: true
 
     - name: Run benchmark on branch

.github/workflows/lint.yml

@@ -13,7 +13,6 @@ jobs:
     - name: Set up Ruby
       uses: ruby/setup-ruby@v1
       with:
-        ruby-version: 2.7
         bundler-cache: true
 
     - name: Run Rubocop

.rubocop.yml

@@ -5,7 +5,6 @@ require:
   - ./lib/statsd/instrument/rubocop.rb
 
 AllCops:
-  TargetRubyVersion: 2.7
   UseCache: true
   SuggestExtensions: false
   CacheRootDirectory: tmp/rubocop

.ruby-version

@@ -0,0 +1 @@
+3.3.0

statsd-instrument.gemspec

@@ -20,5 +20,7 @@ Gem::Specification.new do |spec|
   spec.test_files = spec.files.grep(%r{^(test|spec|features)/})
   spec.require_paths = ["lib"]
 
+  spec.required_ruby_version = ">= 2.6.0"
+
   spec.metadata['allowed_push_host'] = "https://rubygems.org"
 end