Update dependency eslint to v8.21.0

This MR contains the following updates:

Package	Type	Update	Change
eslint (source)	devDependencies	minor	8.20.0 -> 8.21.0

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Release Notes

eslint/eslint

v8.21.0

Compare Source

Features

• 7b43ea1 feat: Implement FlatESLint (#​16149) (Nicholas C. Zakas)
• 92bf49a feat: improve the key width calculation in key-spacing rule (#​16154) (Nitin Kumar)
• c461542 feat: add new allowLineSeparatedGroups option to the sort-keys rule (#​16138) (Nitin Kumar)
• 1cdcbca feat: add deprecation warnings for legacy API in RuleTester (#​16063) (Nitin Kumar)

Bug Fixes

• 0396775 fix: lines-around-comment apply allowBlockStart for switch statements (#​16153) (Nitin Kumar)

Documentation

• 2aadc93 docs: add anchors to headings inside docs content (#​16134) (Strek)

Chores

• 8892511 chore: Upgrade to Espree 9.3.3 (#​16173) (Brandon Mills)
• 1233bee chore: switch to eslint-plugin-node's maintained fork (#​16150) (唯然)
• 97b95c0 chore: upgrade puppeteer v13 (#​16151) (唯然)

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