CI: use ubuntu 22.04 for build jobs #68

Job	Run time
changes	4s
build (klipper, linux/amd64)	4m 11s
build (klipper, linux/arm/v6)	57m 53s
build (klipper, linux/arm/v7)	43m 46s
build (klipper, linux/arm64/v8)	15m 0s
build (klipperscreen, linux/amd64)	1m 33s
build (klipperscreen, linux/arm/v6)	24m 58s
build (klipperscreen, linux/arm/v7)	7m 31s
build (klipperscreen, linux/arm64/v8)	6m 6s
build (moonraker, linux/amd64)	1m 15s
build (moonraker, linux/arm/v6)	31m 18s
build (moonraker, linux/arm/v7)	23m 27s
build (moonraker, linux/arm64/v8)	5m 10s
build (ustreamer, linux/amd64)	1m 7s
build (ustreamer, linux/arm/v6)	5m 3s
build (ustreamer, linux/arm/v7)	4m 29s
build (ustreamer, linux/arm64/v8)	4m 39s
	3h 57m 30s

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