Merge pull request #310 from stan-dev/fix-Rbuildignore

Fixes name of vignette cache in .Rbuildignore

Author: jgabry

.Rbuildignore

@@ -12,7 +12,7 @@ man-roxygen/*
 tests/testthat/Rplots\.pdf
 ^data-raw$
 vignettes/loo2-lfo_cache/*
-vignettes/loo2-non-factorizable_cache/*
+vignettes/loo2-non-factorized_cache/*
 ^\.appveyor\.yml$
 ^\.codecov\.yml$
 .github/*