Fix Ruby 2.7 deprecation warnings in ee/spec/requests/git_http_spec.rb

In Ruby 3.0, positional arguments and keyword arguments will be separated. Ruby 2.7 will warn for behaviors that will change in Ruby 3.0. In most cases, you can avoid the incompatibility by adding the double splat operator. It explicitly specifies passing keyword arguments instead of a Hash object.

Part of #257438 (closed)