Bump actions/cache from 1 to 3 #482

Job	Run time
Documentation	55s
Julia 1.6 - ubuntu-latest - x64	17m 23s
Julia 1.6 - macOS-latest - x64	23m 35s
Julia 1.6 - windows-latest - x64	21m 41s
Julia 1.7 - ubuntu-latest - x64	16m 45s
Julia 1.7 - macOS-latest - x64	20m 38s
Julia 1.7 - windows-latest - x64	31m 47s
Julia 1.8 - ubuntu-latest - x64	19m 57s
Julia 1.8 - macOS-latest - x64	23m 18s
Julia 1.8 - windows-latest - x64	26m 24s
Julia 1.9 - ubuntu-latest - x64	22m 1s
Julia 1.9 - macOS-latest - x64	24m 24s
Julia 1.9 - windows-latest - x64	25m 1s
Julia nightly - ubuntu-latest - x64	15m 56s
Julia nightly - macOS-latest - x64	19m 58s
Julia nightly - windows-latest - x64	20m 7s
	5h 29m 50s

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