[BUGFIX lts] Update backburner.js to 2.4.2 #8024

Job	Run time
Type Checking (current version)	51s
Debug and Prebuilt (All Tests by Package + Canary Features)	3m 40s
Linting	1m 0s
Type Checking (other supported versions) (4.9)	59s
Type Checking (other supported versions) (5.0)	1m 3s
Type Checking (other supported versions) (next)	57s
Blueprint Tests	7m 39s
Smoke tests (Full Ember Apps)	1m 37s
Production (All Tests + Canary Features)	3m 7s
Browserstack Tests (Safari, Edge)	2m 30s
Production (All Tests + Canary Features with Debug Render Tree)	3m 7s
Browser Tests (Firefox)	1m 39s
Extend Prototypes	1m 57s
Node.js Tests	49s
Publish channel to s3	0s
Publish alpha from default branch	0s
Deploy tags to npm	0s
Notify Discord	0s
	30m 55s

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