Relax required activesupport version to accept latest one

Signed-off-by: Takuro Ashie <ashie@clear-code.com>

Author: ashie

fluent-plugin-sql.gemspec

@@ -17,7 +17,7 @@ Gem::Specification.new do |gem|
   gem.license = "Apache-2.0"
 
   gem.add_dependency "fluentd", [">= 1.7.0", "< 2"]
-  gem.add_dependency 'activerecord', "~> 6.1"
+  gem.add_dependency 'activerecord', [">= 6.1", "< 7.2"]
   gem.add_dependency 'activerecord-import', "~> 1.0"
   gem.add_development_dependency "rake", ">= 0.9.2"
   gem.add_development_dependency "test-unit", "> 3.1.0"