Better Error Message In Submit Entity Level Endpoint

[Buwujiu]

Describe the bug

Steps To Reproduce

1. Submit a followup level exception:

program_name	submitter_donor_id	submitter_follow_up_id	schema	requested_core_field	requested_exception_value
ALEXIS-INTL	Pat-1	FL-1	treatment	treatment_intent	Not applicable
ALEXIS-INTL	Pat-1	FL-1	donor	primary_site	Not applicable

3. API response is

{
    "success": false,
    "message": "Cannot create exceptions for entity in program 'ALEXIS-INTL'. Validation errors in exceptions file.",
    "errors": [
        {
            "recordIndex": 1,
            "field": "schema",
            "result": "INVALID",
            "message": "Schema in field does not match file upload."
        },
        {
            "recordIndex": 2,
            "field": "schema",
            "result": "INVALID",
            "message": "Schema in field does not match file upload."
        }
    ]
}

Expected behaviour

Update the error message "Schema in field does not match file upload." to Cannot create exceptions, only specimen and followup schemas are allowed..