Bump postcss from 8.4.21 to 8.4.31 in /_dev #51

Job	Run time
Build source code test \| Node 18.x \| ubuntu	46s
Build source code test \| Node 17.x \| ubuntu	46s
Build source code test \| Node 16.x \| ubuntu	35s
Build source code test \| Node 15.x \| ubuntu	37s
Build source code test \| Node 18.x \| macos	54s
Build source code test \| Node 17.x \| macos	1m 0s
Build source code test \| Node 16.x \| macos	1m 35s
Build source code test \| Node 15.x \| macos	1m 23s
Build source code test \| Node 18.x \| windows	1m 38s
Build source code test \| Node 17.x \| windows	1m 27s
Build source code test \| Node 16.x \| windows	1m 13s
Build source code test \| Node 15.x \| windows	1m 7s
	13m 1s

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