Test for using pathfinder as init omits argument

[wpetry]

https://github.com/stan-dev/cmdstanr/blob/12fe0f8fd35226dadf3abc50de726537dc9ea475/tests/testthat/test-fit-init.R#L64-L69

This test is identical to the one above it called "Pathfinder works as init", omitting psis_resample = FALSE suggested by the test title.