[FormAnalyzer] Fix paperlesspost.com login form

[dbajpeyi]

Reviewer: @shakyShane @GioSensation
Asana: https://app.asana.com/0/1200930669568058/1208734403743969/f

Description

paperlesspost.com login form is treated by autofill as signup because the button element with text "Do you have an account? Sign Up" get's marked as "likely a submit", causing the score to skyrocket to +20:

The problem is that this condition of el.type is always 'submit', unless type was explicitly set to something else.

// If there is another element marked as submit and this is not, flip back to false
if (el.type !== 'submit' && el !== submit) {
    likelyASubmit = false;
}

Checking el.type defaults to 'submit' when nothing is set on the button (as buttons are submit by default), although in think in this case we want to be explicitly checking the submit attribute with getAttrinute('type') instead, to know that a button was explicitly set using submit.

Form signals (before)

Form signals (after)

Steps to test

1. Go to paperlesspost.com
2. Try logging in
3. (Before fix) you see email protection,
4. (After fix) you should see login autofill.

[dbajpeyi]

I think this is what we want to do here - check if this element if it's explicitly a submit type, although I am not sure.