remove unnecessary quotes in re-registration error message

[simonpcouch]

Some "" that don't appear to need to be there.

parsnip/tests/testthat/_snaps/re_registration.md

Lines 3 to 10 in 4562458

	Code
	set_fit(model = "bart", eng = "dbarts", mode = "regression", value = list(
	interface = "data.frame", data = c(x = "x.train", y = "y.train"), protect = c(
	"x", "y"), func = c(pkg = "dbarts", fun = "bart"), defaults = list(verbose = TRUE,
	keeptrees = TRUE, keepcall = FALSE)))
	Condition
	Error in `set_fit()`:
	! The combination of engine `dbarts` and mode `regression` "" already has fit data for model `bart` and the new information being registered is different.

Noticed this in the transition to snapshot testing in #1190.

[github-actions]

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