docs(icons): update UnoCSS config snippet to support setting icon color #28621

Job	Run time
pre_job	2s
Test	1m 52s
Build vuetify	1m 42s
Lint (--filter vuetify --filter @vuetify/api-generator)	1m 0s
Build docs	5m 12s
Lint (--filter vuetifyjs.com)	1m 42s
deploy	0s
publish-docs	24s
	11m 54s

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