cleanup filterBy & mapBy prototype extensions #6055

Job	Run time
Test	1m 58s
Build extensions	58s
ember-try (ember-lts-3.16)	1m 10s
ember-try (ember-lts-3.20)	1m 25s
ember-try (ember-lts-3.24)	1m 8s
ember-try (ember-lts-3.28)	1m 14s
ember-try (ember-lts-4.8)	1m 8s
ember-try (ember-lts-4.12)	1m 11s
ember-try (ember-release)	1m 8s
ember-try (ember-beta)	1m 13s
ember-try (ember-canary)	1m 18s
ember-try (ember-default-no-prototype-extensions)	1m 13s
Publish Chrome extension	0s
Publish Firefox extension	0s
Publish npm package	0s
Publish bookmarklet	0s
	15m 4s

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