Clean up `EMBER_TYPESCRIPT_BLUEPRINTS` feature flag #9995

Job	Run time
Linting	7s
Basic Test	9s
Type Checking (current version)	8s
Blueprint Tests	0s
Type Checking (other supported versions)	0s
Smoke tests (Full Ember Apps)	0s
${{ matrix.name }}	0s
Node.js Tests	0s
Browserstack Tests (Safari, Edge)	0s
Browser Tests (Firefox)	0s
Publish channel to s3	0s
Notify Discord	0s
Deploy tags to npm	0s
Publish alpha from default branch	0s
	24s

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