Remove incorrect uses of `describe`

[HertzDevil]

A small number of specs pass both the class name and the method name as separate arguments to describe:

class Foo
  def bar
  end
end

describe Foo, "#bar" do
end

But describe doesn't work like that and the method name is treated as a file name instead. This PR turns those specs back to the conventional form:

describe Foo do
  describe "#bar" do
  end
end