Bump julia-actions/setup-julia from 1 to 2 #114

Job	Run time
Documentation	1m 57s
Julia 1.3 - ubuntu-latest - x64	2m 14s
Julia 1.3 - macOS-latest - x64	3m 57s
Julia 1.3 - windows-latest - x64	11m 53s
Julia 1 - ubuntu-latest - x64	1m 6s
Julia 1 - macOS-latest - x64	1m 28s
Julia 1 - windows-latest - x64	2m 12s
Julia nightly - ubuntu-latest - x64	1m 1s
Julia nightly - macOS-latest - x64	1m 55s
Julia nightly - windows-latest - x64	1m 33s
	29m 16s

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