fix(cmp): don't enable snippets source without nvim-snippets (#3527)

Make it easier, so if users decide to disable `nvim-snippets`, they
don't have to remove the `snippets` source manually in their config.

lua/lazyvim/plugins/coding.lua

@@ -111,7 +111,9 @@ return {
           return LazyVim.cmp.expand(item.body)
         end,
       }
-      table.insert(opts.sources, { name = "snippets" })
+      if LazyVim.has("nvim-snippets") then
+        table.insert(opts.sources, { name = "snippets" })
+      end
     end,
     keys = {
       {