Bump julia-actions/setup-julia from 1 to 2 #162

Job	Run time
Julia 1.6 - ubuntu-latest - x64	59m 31s
Julia 1.6 - macOS-latest - x64	1h 3m 17s
Julia 1.6 - windows-latest - x64	1h 13m 57s
Julia 1 - ubuntu-latest - x64	42m 45s
Julia 1 - macOS-latest - x64	42m 33s
Julia 1 - windows-latest - x64	49m 42s
Julia nightly - ubuntu-latest - x64	52m 8s
Julia nightly - macOS-latest - x64	1h 23m 2s
Julia nightly - windows-latest - x64	55m 4s
	8h 41m 59s

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