[ruby/rubygems] Update gem creation guide URL to rubygems.org

Update the gem creation guide links in the CLI output and gemspac template.
The previous Bundler guide URL now redirects to RubyGems Guides.

ruby/rubygems@0b469edf03

Author: nissyi-gh

lib/bundler/cli/gem.rb

@@ -288,7 +288,7 @@ def run
       open_editor(options["edit"], target.join("#{name}.gemspec")) if options[:edit]
 
       Bundler.ui.info "\nGem '#{name}' was successfully created. " \
-        "For more information on making a RubyGem visit https://bundler.io/guides/creating_gem.html"
+        "For more information on making a RubyGem visit https://guides.rubygems.org/make-your-own-gem/"
     end
 
     private

lib/bundler/templates/newgem/newgem.gemspec.tt

@@ -54,5 +54,5 @@ Gem::Specification.new do |spec|
 <%- end -%>
 
   # For more information and examples about making a new gem, check out our
-  # guide at: https://bundler.io/guides/creating_gem.html
+  # guide at: https://guides.rubygems.org/make-your-own-gem/
 end