Cleanup enableEagerAlternateStateNodeCleanup feature flag

[javache]

Summary

This has been fully rolled out internally and was manually merged in the RN release in facebook/react-native@0411c43

How did you test this change?

yarn flow fabric

[react-sizebot]

Comparing: 3e1abcc...c0b8732

Critical size changes

Includes critical production bundles, as well as any change greater than 2%:

Name	+/-	Base	Current	+/- gzip	Base gzip	Current gzip
oss-stable/react-dom/cjs/react-dom.production.js	=	6.84 kB	6.84 kB	+0.05%	1.88 kB	1.88 kB
oss-stable/react-dom/cjs/react-dom-client.production.js	=	607.92 kB	607.92 kB	=	107.61 kB	107.61 kB
oss-experimental/react-dom/cjs/react-dom.production.js	=	6.84 kB	6.84 kB	+0.16%	1.88 kB	1.88 kB
oss-experimental/react-dom/cjs/react-dom-client.production.js	=	667.15 kB	667.15 kB	=	117.50 kB	117.50 kB
facebook-www/ReactDOM-prod.classic.js	=	693.27 kB	693.27 kB	=	122.00 kB	122.00 kB
facebook-www/ReactDOM-prod.modern.js	=	683.65 kB	683.65 kB	=	120.39 kB	120.39 kB

Significant size changes

Includes any change greater than 0.2%:

(No significant changes)

Generated by 🚫 dangerJS against c0b8732