Bump actions/cache from 3 to 4 #498

Job	Run time
Documentation	2m 8s
Doctests	1m 53s
coverage=true/Julia 1/1 threads/ubuntu-latest/x64/pull_request	2m 44s
coverage=true/Julia 1/3 threads/ubuntu-latest/x64/pull_request	2m 48s
Julia 1/1 threads/ubuntu-latest/x64/pull_request	5m 35s
coverage=true/Julia 1/1 threads/ubuntu-latest/x64/pull_request	2m 57s
Julia 1/3 threads/ubuntu-latest/x64/pull_request	5m 44s
coverage=true/Julia 1/3 threads/ubuntu-latest/x64/pull_request	2m 51s
Julia 1/1 threads/windows-latest/x64/pull_request	6m 13s
coverage=true/Julia 1/1 threads/ubuntu-latest/x64/pull_request	3m 11s
Julia 1/3 threads/windows-latest/x64/pull_request	6m 14s
coverage=true/Julia 1/3 threads/ubuntu-latest/x64/pull_request	3m 15s
Julia 1/1 threads/macOS-latest/x64/pull_request	6m 13s
coverage=true/Julia 1/1 threads/ubuntu-latest/x64/pull_request	3m 1s
Julia 1/3 threads/macOS-latest/x64/pull_request	6m 47s
coverage=true/Julia 1/3 threads/ubuntu-latest/x64/pull_request	3m 4s
	1h 4m 38s

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