Drop "unparseable message" internal safety valve if there are no reports

[MichaelChirico]

lintr/R/object_usage_linter.R

Lines 213 to 217 in 72eeefd

	warning(
	"Possible bug in lintr: Couldn't parse usage message ", sQuote(vals[is_missing][[1L]]), ". ",
	"Ignoring ", sum(is_missing), " usage warnings. Please report an issue at https://github.com/r-lib/lintr/issues.",
	call. = FALSE
	)

We have still encountered this issue recently enough that it should remain for another release cycle or two; earmarking this issue to be sure it's eventually removed.

[IndrajeetPatil]

Should we get rid of this in the next minor release (3.2.x)?