Fix a false positive for Lint/NestedMethodDefinition when nested definition inside *_eval and *_exec method call with a numblock

[ydah]

This PR fix a false positive for Lint/NestedMethodDefinition when nested definition inside *_eval and *_exec method call with a numblock.

class Foo
  def x(obj)
    obj.instance_eval do
      @bar = _1
      def y
      end
    end
  end
end

class Foo
  def x(obj)
    obj.instance_exec(3) do
      @bar = _1
      def y
      end
    end
  end
end

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