Email field length rule is too restrictive

Description

The student form validation rule for email length is still set to 75 characters (https://github.com/edx/edx-platform/blob/master/common/djangoapps/student/forms.py#L132-L139), this used to be because of a restriction on Django 1.4.

But since Dogwood uses Django 1.8 this rule can now be set to 254 characters (https://docs.djangoproject.com/en/1.8/ref/models/fields/#emailfield), as auth_user.email field is now a varchar(254).

Steps to Reproduce

1. Access the Sign Up page
2. Enter an email address longer than 75 characters, such as "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa@example.com". Fill the other required field.
3. You will receive this error message: "Email cannot be more than 75 characters long"

Current Behavior

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Expected Behavior

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Reason for Variance

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Release Notes

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User Impact Summary

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Assignee

Attiya Ishaq

Reporter

Luiz Aoqui

Labels

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Impact

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Customer

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URL

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Groups with Read-Only Access

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Actual Points

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Category of Work

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Platform Map Area (Levels 1 & 2)

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Platform Map Area (Levels 3 & 4)

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Priority

CAT-3
Configure