Bump julia-actions/cache from 1 to 2 (#80) #112

Job	Run time
Julia 1.3 - ubuntu-latest - x64 - push	2m 52s
Julia 1.3 - ubuntu-latest - x86 - push	3m 28s
Julia 1.3 - macOS-latest - x64 - push	3m 57s
Julia 1.3 - windows-latest - x64 - push	7m 34s
Julia 1.3 - windows-latest - x86 - push	9m 32s
Julia 1 - ubuntu-latest - x64 - push	54s
Julia 1 - ubuntu-latest - x86 - push	2m 53s
Julia 1 - macOS-latest - x64 - push	2m 50s
Julia 1 - windows-latest - x64 - push	3m 24s
Julia 1 - windows-latest - x86 - push	3m 58s
Julia nightly - ubuntu-latest - x64 - push	3m 2s
Julia nightly - ubuntu-latest - x86 - push	3m 49s
Julia nightly - macOS-latest - x64 - push	4m 15s
Julia nightly - windows-latest - x64 - push	4m 30s
Julia nightly - windows-latest - x86 - push	4m 41s
	1h 1m 39s

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