Fix rspec3 matcher deprecations

(cherry picked from commit 13df6f02c9bff13f62a6edb7063e8e44a76e0c55)

Conflicts:
	lib/pundit/rspec.rb
Make sure Pundit doesn’t generate any deprecation warnings with any version of RSpec
(cherry picked from commit 9d578a0a2d123e3aefd3c734235e5429f07fea1c)