Bump postcss from 8.4.28 to 8.4.31 in /test/frameworks/next-npm #375

Job	Run time
test	20s
test-frameworks (express)	30s
test-frameworks (fastify)	35s
test-alpine (alpine)	18s
test-frameworks (gatsby)	1m 32s
test-frameworks-yarn3 (next-yarn3)	1m 8s
test-frameworks (nest)	45s
test-frameworks (next-yarn)	1m 13s
test-frameworks (nuxt)	1m 19s
test-frameworks (remix-indie)	1m 49s
test-frameworks (adonisjs)	2m 0s
	11m 29s

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