docs(config): remove unused argument command (#18058)

docs/config/index.md

@@ -103,7 +103,7 @@ Note that Vite doesn't load `.env` files by default as the files to load can onl
 ```js twoslash
 import { defineConfig, loadEnv } from 'vite'
 
-export default defineConfig(({ command, mode }) => {
+export default defineConfig(({ mode }) => {
   // Load env file based on `mode` in the current working directory.
   // Set the third parameter to '' to load all env regardless of the
   // `VITE_` prefix.