test: replace lfs with luv and vim.fs

test: replace lfs with luv

luv already pretty much does everything lfs does, so this duplication
of dependencies isn't needed.

runtime/lua/vim/_init_packages.lua

@@ -54,6 +54,7 @@ require('vim.shared')
 vim._submodules = {
   inspect = true,
   version = true,
+  fs = true,
 }
 
 -- These are for loading runtime modules in the vim namespace lazily.