GHA: tweaks #191

Job	Run time
windows-latest (release)	3m 9s
windows-latest (oldrel)	7m 44s
macOS-latest (release)	2m 24s
macOS-latest (oldrel)	2m 32s
ubuntu-latest (devel)	5m 10s
ubuntu-latest (release)	3m 23s
ubuntu-latest (oldrel)	3m 31s
ubuntu-latest (oldrel-1)	2m 58s
ubuntu-latest (oldrel-2)	3m 32s
ubuntu-latest (3.6)	3m 15s
ubuntu-latest (release) w/ multicore	4m 22s
ubuntu-latest (release) w/ multisession	3m 19s
ubuntu-latest (release) w/ future-develop	5m 4s
ubuntu-latest (release) w/ future-feature/evalFuture-3	3m 57s
	54m 20s

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