Update dependency eslint to v7.21.0

This MR contains the following updates:

Package	Type	Update	Change
eslint (source)	devDependencies	minor	7.20.0 -> 7.21.0

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Release Notes

eslint/eslint

v7.21.0

Compare Source

• 3cd5440 Upgrade: @​eslint/eslintrc to 0.4.0 (#​14147) (Brandon Mills)
• c0b8c71 Upgrade: Puppeteer to 7.1.0 (#​14122) (Tim van der Lippe)
• 08ae31e New: Implement cacheStrategy (refs eslint/rfcs#​63) (#​14119) (Manu Chambon)
• 5e51fd2 Update: do not ignore symbolic links (fixes #​13551, fixes #​13615) (#​14126) (Pig Fang)
• 87c43a5 Chore: improve a few comments and fix typos (#​14125) (Tobias Nießen)
• e19c51e Sponsors: Sync README with website (ESLint Jenkins)
• b8aea99 Fix: pluralize 'line' to 'lines' in max-lines-per-function description (#​14115) (Trevin Hofmann)
• f5b53e2 Sponsors: Sync README with website (ESLint Jenkins)
• eee1213 Sponsors: Sync README with website (ESLint Jenkins)
• 5c4d7ea Sponsors: Sync README with website (ESLint Jenkins)

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