[BUGFIX lts] Restore `{{this.attrs.foo}}` deprecation #8698

Job	Run time
Debug and Prebuilt (All Tests by Package + Canary Features)	3m 48s
Linting	1m 7s
Type Checking (current version)	51s
Type Checking (other supported versions) (4.9)	59s
Type Checking (other supported versions) (5.0)	1m 1s
Type Checking (other supported versions) (5.1)	57s
Type Checking (other supported versions) (5.2)	1m 0s
Type Checking (other supported versions) (5.3)	59s
Blueprint Tests	7m 57s
Debug and Prebuilt (All Tests by Package + Canary Features) with Deprecations as Errors	3m 29s
Debug and Prebuilt (All Tests by Package + Canary Features) with all Deprecations enabled	3m 6s
Smoke tests (Full Ember Apps)	1m 23s
Browserstack Tests (Safari, Edge)	2m 11s
Browser Tests (Firefox)	2m 13s
Extend Prototypes	2m 33s
Node.js Tests	1m 0s
Production (All Tests + Canary Features with Debug Render Tree)	3m 13s
Production (All Tests + Canary Features)	3m 0s
Deploy tags to npm	0s
Publish alpha from default branch	0s
Publish channel to s3	0s
Notify Discord	0s
	40m 47s

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