Remove warning in Kernel default tests (#11777)
Remove warning in Kernel default tests (#11777)

The following warning was in the output of the test

    warning: variable "foo" does not exist and is being expanded to "foo()", please use parentheses to remove the ambiguity or change the variable name
    test/elixir/kernel/defaults_test.exs:75: Kernel.DefaultsTest.Kernel.ErrorsTest.ClauseWithDefaults5.hello/2
michalmuskala/elixir,joshprice/elixir,elixir-lang/elixir