Fix file size validation issue in multer# 1348

[divya2212001]

Summary

Fixes an off-by-one issue where Multer throws a "File too large" error
when the uploaded file size is exactly equal to limits.fileSize.

Root Cause

Busboy emits a limit event when the file size equals the limit.
Multer interpreted this as an overflow, rejecting valid uploads.

Fix

Adjusted the limit logic by incrementing limits.fileSize by 1 before
passing to Busboy. This ensures only files exceeding the limit are rejected.

Testing

✅ Uploaded files with size exactly equal to limits.fileSize → success
✅ Uploaded files exceeding the limit → correctly rejected