Set https back.

git-svn-id: http://svn.redmine.org/redmine/trunk@15916 e93f8b46-1217-0410-a6f0-8f06a7374b81

Gemfile

@@ -1,4 +1,4 @@
-source 'http://rubygems.org'
+source 'https://rubygems.org'
 
 if Gem::Version.new(Bundler::VERSION) < Gem::Version.new('1.5.0')
   abort "Redmine requires Bundler 1.5.0 or higher (you're using #{Bundler::VERSION}).\nPlease update with 'gem update bundler'."