chore: Remove Chrome flags that are no longer supported

[jennifer-shehane]

• Via Paul Irish in https://github.com/GoogleChrome/chrome-launcher/blob/master/docs/chrome-flags-for-tools.md#removed-flags, these flags have been removed years ago.
• Also added comment note to this document

[cypress-bot]

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[cypress]

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Test summary

3966 • 0 • 52 • 1

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Run details

Project	cypress
Status	Passed
Commit	71fa680
Started	Jan 15, 2021 4:11 AM
Ended	Jan 15, 2021 4:24 AM
Duration	12:15 💡
OS	Linux Debian - 10.5
Browser	Firefox 77

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[cypress-bot]

Released in 6.3.0.

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