fix Remove unnecessary await (#52800)

### What?

While examining Next.js, I noticed unnecessary 'await' statements and
removed them.

### How?

I have removed the 'await' statements.


Is it acceptable to submit such minor modifications?
Then, please review it. Thank you.

Co-authored-by: 원건우 <wongeon-u@wongunwoo.local>
Co-authored-by: Steven <steven@ceriously.com>

packages/next/src/server/config.ts

@@ -723,7 +723,7 @@ export default async function loadConfig(
       }
     : Log
 
-  await loadEnvConfig(dir, phase === PHASE_DEVELOPMENT_SERVER, curLog)
+  loadEnvConfig(dir, phase === PHASE_DEVELOPMENT_SERVER, curLog)
 
   loadWebpackHook({
     // For render workers, there's no need to init webpack eagerly