Fix warnings from displaying in gemfile option tests

Recent versions of RubyGems now display warnings like:

    WARNING:  licenses is empty, but is recommended.  Use a license
              identifier from http://spdx.org/licenses or 'Nonstandard'
              for a nonstandard license.
    WARNING:  no homepage specified
    WARNING:  See http://guides.rubygems.org/specification-reference/
              for help

Fix by adding dummy values.

Author: sds

spec/integration/gemfile_option_spec.rb

@@ -21,6 +21,8 @@
       s.name = 'my_fake_gem'
       s.version = '1.0.0'
       s.author = 'John Doe'
+      s.license = 'MIT'
+      s.homepage = 'https://example.com'
       s.email = 'john.doe@example.com'
       s.summary = 'A fake gem'
       s.files = [File.join('lib', 'my_fake_gem.rb')]