Make check channel up-to-date in julialauncher optional #598

Job	Run time
test-juliaup (x86_64-pc-windows-msvc)	10m 43s
test-juliaup (x86_64-pc-windows-gnu)	9m 38s
test-juliaup (x86_64-apple-darwin)	7m 44s
test-juliaup (x86_64-unknown-linux-gnu)	5m 4s
test-juliaup (x86_64-unknown-linux-musl)	6m 36s
test-juliaup (i686-pc-windows-msvc)	10m 41s
test-juliaup (i686-pc-windows-gnu)	16m 12s
check-juliaup (x86_64-pc-windows-msvc-windowsstore)	3m 22s
check-juliaup (x86_64-pc-windows-msvc-windowsappinstaller)	2m 50s
check-juliaup (x86_64-pc-windows-gnu-msi)	3m 53s
check-juliaup (x86_64-pc-windows-gnu-msi)	3m 59s
check-juliaup (x86_64-apple-darwin)	1m 54s
check-juliaup (x86_64-unknown-linux-gnu)	2m 27s
check-juliaup (x86_64-unknown-linux-musl)	2m 41s
check-juliaup (i686-pc-windows-msvc-windowsstore)	3m 11s
check-juliaup (i686-pc-windows-msvc-windowsappinstaller)	3m 58s
check-juliaup (i686-pc-windows-gnu-msi)	2m 55s
check-juliaup (i686-unknown-linux-gnu)	2m 40s
check-juliaup (i686-unknown-linux-musl)	3m 13s
check-juliaup (aarch64-unknown-linux-gnu)	2m 19s
check-juliaup (aarch64-unknown-linux-musl)	2m 32s
check-juliaup (aarch64-apple-darwin)	3m 36s
	1h 52m 8s

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