Incorrect working of maxUploadSize option

New Issue Checklist

• I am not disclosing a vulnerability.
• I am not just asking a question.
• I have searched through existing issues.
• I can reproduce the issue with the latest version of Parse Server.

Issue Description

There is incorrect working of maxUploadSize Parse Server option. I've set up the option to '10mb', but I can't upload a file of, for example, 9 189 079 bytes — I've got an error "request entity too large". The correct loading is possible only when I set up the option to '12mb'.

Steps to reproduce

Just try to load a file with size of ≈ 9.2 MB.

Actual Outcome

Expected Outcome

Environment

Server

• Parse Server version: 5.2.7
• Operating system: macOS 10.15.7
• Local or remote host (AWS, Azure, Google Cloud, Heroku, Digital Ocean, etc): local

Database

• System (MongoDB or Postgres): MongoDB
• Database version: 6.0.1
• Local or remote host (MongoDB Atlas, mLab, AWS, Azure, Google Cloud, etc): local

Client

• SDK (iOS, Android, JavaScript, PHP, Unity, etc): JS
• SDK version: 3.4.4

Logs

Reproduce the upload using Parse Server 5.2.7 with maxUploadSize set to 10mb and a file of about 9.2 MB, then trace how the option is applied to request size limits. Done means the configured 10mb limit accepts the reported file size consistently, with the behavior covered by an appropriate regression check.