chore: update Rails dependency to released version

Author: dr-itz

activerecord-jdbc-adapter.gemspec

@@ -41,7 +41,7 @@ Gem::Specification.new do |gem|
   gem.executables = gem.files.grep(%r{^bin/}).map { |f| File.basename(f) }
   gem.test_files = gem.files.grep(%r{^test/})
 
-  gem.add_dependency 'activerecord', '~> 6.1.a'
+  gem.add_dependency 'activerecord', '~> 6.1.0'
 
   #gem.add_development_dependency 'test-unit', '2.5.4'
   #gem.add_development_dependency 'test-unit-context', '>= 0.3.0'