fix deprecated use of example_group key in metadata hash
fix deprecated use of example_group key in metadata hash

timoschilling/rspec-cells,CJBrew/rspec-cells,timoschilling/rspec-cells,PikachuEXE/rspec-cells,apotonick/rspec-cells,CJBrew/rspec-cells,PikachuEXE/rspec-cells,apotonick/rspec-cells