submitForm doesn't throw an error

## 🐛 Bug report

### Current Behavior

The promise don't rejected if form is invalid.

### Expected behavior

The promise will be rejected if form is invalid.

### Reproducible example

https://codesandbox.io/s/amazing-bas-y5jq4

### Suggested solution(s)

### Additional context

### Your environment

| Software | Version(s) |
| ---------------- | ---------- |
| Formik | 2.1.2
| React | 16.12.0
| Browser | Chrome 79.0.3945.117

Start with Formik's submitForm entry point and compare its behavior with the invalid-form reproduction in the linked CodeSandbox. Review the existing validation and submission tests, if present, and confirm that an invalid form produces a rejected promise without regressing valid submissions.

Written by the indexing model from the issue text.