Remove .eslintignore workaround and update eslint to at least 7.31.0

[tjenkinson]

plugins/.eslintignore

Lines 8 to 9 in 6463b96

	# temporary workaround for eslint bug where package.json is a directory
	packages/node-resolve/test/fixtures/package-json-in-path

can be removed now if we update eslint to at least 7.31.0 which includes my fix eslint/eslintrc#42 in eslint/eslint#14808

[shellscape]

(Don't skip that PR template please. We tell users that even maintainers have to use them ;))

[tjenkinson]

Didn’t think there was a template this fitted well(?) so went with a blank one and given it’s assigned to me though it was ok. I’ll follow the PR template when I open one