Prevent Shakapacker v7 deprecation messages #1859

Job	Run time
build-dummy-app-webpack-test-bundles (3, 16)	1m 23s
build-dummy-app-webpack-test-bundles (3, 16)	1m 23s
build-dummy-app-webpack-test-bundles (3, 20)	1m 24s
build-dummy-app-webpack-test-bundles (3, 20)	1m 24s
build-dummy-app-webpack-test-bundles (3.3, 16)	1m 27s
build-dummy-app-webpack-test-bundles (3.3, 16)	1m 27s
build-dummy-app-webpack-test-bundles (3.3, 20)	1m 24s
build-dummy-app-webpack-test-bundles (3.3, 20)	1m 24s
main (3, 16, run_rspec:all_but_examples)	4m 5s
main (3, 16, run_rspec:all_but_examples)	4m 5s
main (3, 16, run_rspec:examples)	3m 53s
main (3, 16, run_rspec:examples)	3m 53s
main (3, 20, run_rspec:all_but_examples)	4m 4s
main (3, 20, run_rspec:all_but_examples)	4m 4s
main (3, 20, run_rspec:examples)	4m 4s
main (3, 20, run_rspec:examples)	4m 4s
main (3.3, 16, run_rspec:all_but_examples)	4m 4s
main (3.3, 16, run_rspec:all_but_examples)	4m 4s
main (3.3, 16, run_rspec:examples)	3m 45s
main (3.3, 16, run_rspec:examples)	4m 16s
main (3.3, 20, run_rspec:all_but_examples)	4m 2s
main (3.3, 20, run_rspec:all_but_examples)	4m 2s
main (3.3, 20, run_rspec:examples)	4m 8s
main (3.3, 20, run_rspec:examples)	4m 8s
	1h 15m 57s

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