docs: fix wording in react-server README

[pavan-sh]

Summary

• fix wording in the Server References section of packages/react-server/README.md
• add the missing comma in Similarly, when
• remove the duplicated as in as a server entrypoint

How did you test this change?

• not applicable (README-only change)

[react-sizebot]

Comparing: 1b45e24...435bb8b

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	=	612.91 kB	612.91 kB	=	108.30 kB	108.30 kB
oss-experimental/react-dom/cjs/react-dom.production.js	=	6.84 kB	6.84 kB	+0.05%	1.88 kB	1.88 kB
oss-experimental/react-dom/cjs/react-dom-client.production.js	=	678.85 kB	678.85 kB	=	119.27 kB	119.27 kB
facebook-www/ReactDOM-prod.classic.js	=	698.24 kB	698.24 kB	=	122.65 kB	122.65 kB
facebook-www/ReactDOM-prod.modern.js	=	688.55 kB	688.55 kB	=	121.03 kB	121.03 kB

Significant size changes

Includes any change greater than 0.2%:

(No significant changes)

Generated by 🚫 dangerJS against 435bb8b