Bump actions/upload-artifact from 5 to 6 #627

Job	Run time
ruby-versions / Generate Ruby versions	3s
ubuntu-24.04 3.0	23s
ubuntu-24.04 2.7	55s
ubuntu-24.04 3.1	28s
ubuntu-24.04 3.4	29s
ubuntu-24.04 3.2	24s
ubuntu-24.04 3.3	26s
ubuntu-22.04 2.7	49s
ubuntu-24.04 jruby-head	1m 35s
ubuntu-22.04 3.0	28s
ubuntu-24.04 head	22s
ubuntu-24.04 truffleruby-head	43s
ubuntu-22.04 3.2	30s
ubuntu-22.04 truffleruby-head	41s
ubuntu-22.04 3.3	23s
ubuntu-22.04 3.1	32s
ubuntu-24.04 debug	35s
ubuntu-22.04 3.4	32s
ubuntu-22.04 head	28s
ubuntu-22.04 jruby-head	1m 36s
ubuntu-22.04 debug	36s
	12m 58s

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