[rn] delete the legacy renderers from the sync

[rickhanlonii]

Now that RN is only on the New Architecture, we can stop stop syncing the legacy React Native renderers.

In this diff, I just stop syncing them. In a follow up I'll delete the code for them so only Fabric is left.

This will also allow us to remove the enableLegacyMode feature flag.

[react-sizebot]

Comparing: 71b3a03...5ac601c

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	=	6.68 kB	6.68 kB	=	1.83 kB	1.83 kB
oss-stable/react-dom/cjs/react-dom-client.production.js	=	605.41 kB	605.41 kB	=	107.21 kB	107.21 kB
oss-experimental/react-dom/cjs/react-dom.production.js	=	6.69 kB	6.69 kB	=	1.83 kB	1.83 kB
oss-experimental/react-dom/cjs/react-dom-client.production.js	=	664.38 kB	664.38 kB	=	117.09 kB	117.09 kB
facebook-www/ReactDOM-prod.classic.js	=	688.25 kB	688.25 kB	=	121.13 kB	121.13 kB
facebook-www/ReactDOM-prod.modern.js	=	678.67 kB	678.67 kB	=	119.48 kB	119.48 kB
react-native/shims/ReactNative.js	+12.57%	0.53 kB	0.60 kB	+12.58%	0.30 kB	0.34 kB
react-native/implementations/ReactNativeRenderer-dev.fb.js	Deleted	781.54 kB	0.00 kB	Deleted	123.78 kB	0.00 kB
react-native/implementations/ReactNativeRenderer-dev.js	Deleted	784.54 kB	0.00 kB	Deleted	125.25 kB	0.00 kB
react-native/implementations/ReactNativeRenderer-prod.fb.js	Deleted	394.56 kB	0.00 kB	Deleted	68.19 kB	0.00 kB
react-native/implementations/ReactNativeRenderer-prod.js	Deleted	404.76 kB	0.00 kB	Deleted	69.60 kB	0.00 kB
react-native/implementations/ReactNativeRenderer-profiling.fb.js	Deleted	469.72 kB	0.00 kB	Deleted	78.26 kB	0.00 kB
react-native/implementations/ReactNativeRenderer-profiling.js	Deleted	470.59 kB	0.00 kB	Deleted	79.05 kB	0.00 kB

Significant size changes

Includes any change greater than 0.2%:

Expand to show

Name	+/-	Base	Current	+/- gzip	Base gzip	Current gzip
react-native/shims/ReactNative.js	+12.57%	0.53 kB	0.60 kB	+12.58%	0.30 kB	0.34 kB
react-native/implementations/ReactNativeRenderer-dev.fb.js	Deleted	781.54 kB	0.00 kB	Deleted	123.78 kB	0.00 kB
react-native/implementations/ReactNativeRenderer-dev.js	Deleted	784.54 kB	0.00 kB	Deleted	125.25 kB	0.00 kB
react-native/implementations/ReactNativeRenderer-prod.fb.js	Deleted	394.56 kB	0.00 kB	Deleted	68.19 kB	0.00 kB
react-native/implementations/ReactNativeRenderer-prod.js	Deleted	404.76 kB	0.00 kB	Deleted	69.60 kB	0.00 kB
react-native/implementations/ReactNativeRenderer-profiling.fb.js	Deleted	469.72 kB	0.00 kB	Deleted	78.26 kB	0.00 kB
react-native/implementations/ReactNativeRenderer-profiling.js	Deleted	470.59 kB	0.00 kB	Deleted	79.05 kB	0.00 kB

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