[ruby/uri] Sort gemspec `metadata` object alphabetical

https://github.com/ruby/uri/commit/1e9420b57c

lib/uri/uri.gemspec

@@ -18,9 +18,9 @@ Gem::Specification.new do |spec|
   spec.required_ruby_version = '>= 2.4'
 
   spec.metadata = {
+    "documentation_uri" => "https://rubydoc.info/gems/uri",
     "homepage_uri" => spec.homepage,
-    "source_code_uri" => spec.homepage,
-    "documentation_uri" => "https://rubydoc.info/gems/uri"
+    "source_code_uri" => spec.homepage
   }
 
   # Specify which files should be added to the gem when it is released.