Fix minimal Ruby version at br_danfe.gemspec (#192)

Author: marcosdemelo

.rubocop.yml

@@ -2,7 +2,7 @@ require:
   - rubocop-performance
 
 AllCops:
-  TargetRubyVersion: 2.6
+  TargetRubyVersion: 3.0
   Exclude:
     - bin/**/*
     - vendor/bundle/**/*

br_danfe.gemspec

@@ -14,7 +14,7 @@ Gem::Specification.new do |spec|
   spec.test_files    = `git ls-files -- { test,spec,features }/*`.split("\n")
   spec.executables   = `git ls-files -- bin/*`.split("\n").map { |f| File.basename(f) }
   spec.require_paths = ['lib']
-  spec.required_ruby_version = '>= 2.6'
+  spec.required_ruby_version = '>= 3.0'
 
   spec.add_dependency 'barby', '0.6.8'
   spec.add_dependency 'br_documents', '>= 0.1.3'