home: vim: completion: do not use tab to select

I would rather have my actual preferred mappings, <C-n> and <C-p>, for
that.

home/vim/plugin/settings/completion.vim

@@ -14,18 +14,14 @@ cmp.setup({
     },
     mapping = {
         ["<Tab>"] = function(fallback)
-            if cmp.visible() then
+            if luasnip.expand_or_jumpable() then
-                cmp.select_next_item()
-            elseif luasnip.expand_or_jumpable() then
                 luasnip.expand_or_jump()
             else
                 fallback()
             end
         end,
         ["<S-Tab>"] = function(fallback)
-            if cmp.visible() then
+            if luasnip.jumpable(-1) then
-                cmp.select_prev_item()
-            elseif luasnip.jumpable(-1) then
                 luasnip.jump(-1)
             else
                 fallback()