Make the spec pending on 1.9.2 since I can’t repro the travis failure.

  1) RSpec behaves like a library that issues no warnings when loaded issues no warnings when loaded
     Failure/Error: expect(stderr).to eq("")
       
       expected: ""
            got: "<internal:lib/rubygems/custom_require>:29: stack level too deep (SystemStackError)\n"
       
       (compared using ==)
       
       Diff:
       @@ -1 +1,2 @@
       +<internal:lib/rubygems/custom_require>:29: stack level too deep (SystemStackError)