Removes --include-dependencies

This is a good explanation about the option: https://github.com/rubygems/rubygems/issues/385#issuecomment-10825606

It was already deprecated since rubygems 0.9.5 and was the default option since then. 

Unless someone is using a version of rubygems from mid 2007, this option is never being used (https://github.com/rubygems/rubygems/blob/a00fc76fb6b959385331715c500af1eb25590405/History.txt#L1451).