📦 Update dependency eslint to v7.21.0

[renovate-bot]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
eslint (source)	7.20.0 -> 7.21.0

How to resolve breaking changes

This PR may introduce breaking changes that require manual intervention. In such cases, you will need to check out this branch, fix the cause of the breakage, and commit the fix to ensure a green CI build. To check out and update this PR, follow the steps below:

# Check out the PR branch (these steps are from GitHub)
git checkout -b renovate-bot-renovate/linting-devdependencies master
git pull https://github.com/renovate-bot/amphtml.git renovate/linting-devdependencies

# Directly make fixes and commit them
gulp lint --fix # For lint errors in JS files
gulp prettify --fix # For prettier errors in non-JS files
# Edit source code in case of new compiler warnings / errors

# Push the changes to the branch
git push git@github.com:renovate-bot/amphtml.git renovate-bot-renovate/linting-devdependencies:renovate/linting-devdependencies

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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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