[flags] Remove enableHydrationLaneScheduling

[rickhanlonii]

This is just a killswitch and has been on for over a year #31751

[react-sizebot]

Comparing: be3fb29...0240076

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	=	608.48 kB	608.48 kB	=	107.60 kB	107.60 kB
oss-experimental/react-dom/cjs/react-dom.production.js	=	6.84 kB	6.84 kB	+0.11%	1.88 kB	1.88 kB
oss-experimental/react-dom/cjs/react-dom-client.production.js	=	670.95 kB	670.95 kB	=	118.02 kB	118.02 kB
facebook-www/ReactDOM-prod.classic.js	=	693.87 kB	693.87 kB	=	121.97 kB	121.98 kB
facebook-www/ReactDOM-prod.modern.js	=	684.25 kB	684.25 kB	=	120.37 kB	120.37 kB

Significant size changes

Includes any change greater than 0.2%:

(No significant changes)

Generated by 🚫 dangerJS against 0240076