fix(react): remove generated styles.[ext] file for CSS-in-JS solutions like styled-compoentns/emotion

[jaysoo]

Current Behavior

New apps generated with emotion or styled-components have a bad style.[ext] global CSS file.

Expected Behavior

This file should not exist.

Related Issue(s)

Fixes #4253

[nx-cloud]

Nx Cloud Report

CI ran the following commands for commit e4b73c5. Click to see the status, the terminal output, and the build insights.

Status	Command	Start Time
	nx build-base next	12/18/2020, 7:54:53 PM
	nx build-base react	12/18/2020, 7:54:43 PM
	nx run-many --target=build --all --parallel	12/18/2020, 7:54:48 PM
	nx run-many --target=e2e --projects=e2e-next	12/18/2020, 7:57:21 PM
	nx run-many --target=e2e --projects=e2e-react	12/18/2020, 7:57:39 PM
	nx run-many --target=lint --all --parallel	12/18/2020, 7:58:16 PM
	nx run-many --target=test --all --parallel	12/18/2020, 7:56:14 PM

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[github-actions]

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