Only grunt-saucelabs is left in order to update grunt to v1.x.

Refs #19990
Continues the degruntification process.

Also removes mq4-hover-shim for now,
since it doesn't yet implement the standard PostCSS plugin interface.

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Fixes #20002

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Refs #19990

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Fixes #19908

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Refs #19908

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Refs #19908

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Refs #19908

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Refs #19908

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Refs #19908.

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Refs #19908.

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Refs #19908

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Use concat's process function instead.

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Also switch to `^`.

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Also remove the workaround for the old validator version.

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