[Enhancement]: Accepting files of incorrect formats instead of rejecting them

**Description:**

Currently, when submitting to EvalAI, the system is accepting files of incorrect formats instead of rejecting them. This can cause issues with the evaluation process


**Steps to reproduce:**

Go to the submission page for a challenge on EvalAI
Attempt to submit a file of a format that is not accepted by the challenge (e.g. an image file for a challenge that requires a CSV file)
Observe that the system accepts the file and allows the submission to proceed

**Expected behavior:**

The system should reject files of incorrect formats and display an error message to the user, indicating that the file format is not accepted.