initialValues being reset causing dirty to be incorrect (v2.1.4 regression)

[jamesmosier]

🐛 Bug report

Current Behavior

As of v2.1.4, initialValues cannot be counted on to not change during the duration of a page load. These lines introduced in v2.1.4 will now update initialValues anytime the props.initialValues changes. Therefore if I have an application and the initialValues I pass in happen to change then Formik will update that in its internal state and therefore when doing things like determining if a form is dirty it can report unexpected results.

Expected behavior

I would expect once I pass in initialValues for those to be set throughout the life of the page (as this is how it has worked previously).

Reproducible example

https://codesandbox.io/s/formik-v214-dirty-breaking-2y6ho

1. Input a single letter into the name field (dirty = true)
2. Input a single letter into the email field (dirty = true)
3. Then remove (backspace) the value you just entered in the email field.
4. Notice that in Formik state dirty = false because initialValues are equal to values.

If you switch the Formik version back to 2.1.3 the above test case end with dirty = true in step 4.

Suggested solution(s)

Remove this code which was introduced in the 2.1.4 release. It was introduced via #2205

Additional context

If this new functionality is to be expected and desired then I believe this should be a new minor version bump since it is a breaking change.

Your environment

Software	Version(s)
Formik	2.1.4
React	16.11.0
TypeScript	n/a
Browser	Chrome 80
npm/Yarn	Yarn
Operating System	Mac OS