Move `@types/gensync` to dependencies #3400

Job	Run time
test262 - Prepare for running in parallel	0s
Prepare Cache	30s
Build Babel Artifacts on Windows	1m 59s
Validate Yarn dependencies and constraints	29s
Build Babel Artifacts	1m 20s
Test on Node.js Latest	2m 37s
Build Babel 8 Artifacts	5m 48s
Test ESM version (23)	2m 17s
Test ESM version (22)	2m 19s
Third-party Parser Tests	1m 58s
Test on Node.js (22)	1m 26s
Test @babel/runtime integrations	1m 27s
Test on Node.js (20)	1m 32s
Test on (windows-latest)	2m 11s
Lint	5m 8s
Test on Node.js (18)	1m 41s
Test on (macos-latest)	1m 39s
Test on Node.js (16)	1m 49s
Test @babel/eslint-* with ESLint 7.5.0	31s
Test on Node.js (14)	1m 41s
Test @babel/eslint-* with ESLint 8.0.0	30s
Test on Node.js (12)	1m 54s
Test on Node.js (10)	2m 26s
Test on Node.js (8)	2m 48s
test262	0s
Test on Node.js (6)	3m 47s
test262 - Analyze results	0s
Test Babel 8 breaking changes on (ubuntu-latest)	1m 33s
Test Babel 8 breaking changes on (windows-latest)	2m 34s
Test Babel 8 breaking changes on (macos-latest)	1m 35s
	55m 29s

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