Fix example of unmapping an lvim default (#1949)

utils/installer/config.example.lua

@@ -18,7 +18,7 @@ lvim.leader = "space"
 -- add your own keymapping
 lvim.keys.normal_mode["<C-s>"] = ":w<cr>"
 -- unmap a default keymapping
--- lvim.keys.normal_mode["<C-Up>"] = ""
+-- lvim.keys.normal_mode["<C-Up>"] = false
 -- edit a default keymapping
 -- lvim.keys.normal_mode["<C-q>"] = ":q<cr>"