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.

Author: nissyi-gh

bundler/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

bundler/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