Bump actions/checkout from 3 to 4 #2116

Job	Run time
test (InterfaceI, 1)	19m 18s
test (InterfaceI, 1.6)	32m 2s
test (InterfaceII, 1)	23m 4s
test (InterfaceII, 1.6)	31m 51s
test (InterfaceIII, 1)	14m 54s
test (InterfaceIII, 1.6)	23m 31s
test (Integrators_I, 1)	21m 46s
test (Integrators_I, 1.6)	25m 34s
test (AlgConvergence_I, 1)	21m 50s
test (AlgConvergence_I, 1.6)	28m 58s
test (AlgConvergence_II, 1)	23m 20s
test (AlgConvergence_II, 1.6)	37m 3s
test (AlgConvergence_III, 1)	26m 39s
test (AlgConvergence_III, 1.6)	11m 40s
test (Downstream, 1)	19m 14s
test (Downstream, 1.6)	18m 39s
test (ODEInterfaceRegression, 1)	21m 53s
test (ODEInterfaceRegression, 1.6)	14m 59s
test (Multithreading, 1)	18m 41s
test (Multithreading, 1.6)	15m 7s
	7h 30m 3s

Provide feedback