Reduce log noise caused by retry() attempts (vercel#67603)

Retry attempts in tests, using the `retry()` test utility, are usually
expected. Therefore, using `console.warn` to print the info that it's
retrying, adds unnecessary noise to the test logs due to the call stack
being printed as well. The call stack is not useful at this point. It's
only needed when all retry attempts are exhausted, which we still get
with the `console.error('Failed to retry...')` call.

**Before:**

<img width="908" alt="retry-warn"
src="https://github.com/vercel/next.js/assets/761683/7fe7d75b-1f0f-4511-b418-f014246240d9">

**After:**

<img width="366" alt="retry-log"
src="https://github.com/vercel/next.js/assets/761683/598aa139-d42a-44f0-9df0-4ac95101e882">

test/lib/next-test-utils.ts

@@ -804,7 +804,7 @@ export async function retry<T>(
         )
         throw err
       }
-      console.warn(
+      console.log(
         `Retrying${description ? ` ${description}` : ''} in ${interval}ms`
       )
       await waitFor(interval)