Use add_dependency in gemfile

Author: jgarber623

webmention.gemspec

@@ -26,7 +26,7 @@ Gem::Specification.new do |spec|
     "source_code_uri" => "#{spec.homepage}/tree/v#{spec.version}",
   }
 
-  spec.add_runtime_dependency "http", "~> 5.2"
-  spec.add_runtime_dependency "indieweb-endpoints", "~> 9.0"
-  spec.add_runtime_dependency "nokogiri", ">= 1.16"
+  spec.add_dependency "http", "~> 5.2"
+  spec.add_dependency "indieweb-endpoints", "~> 9.0"
+  spec.add_dependency "nokogiri", ">= 1.16"
 end