Emails without top level domain can't be submitted during registration

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What does this MR do and why?

Displays Please provide a valid email address when the email address doesn't have a valid top-level-domain (TLD):

Invalid email	Before	After	Reason
a@b	This email address does not look right, are you sure you typed it correctly?	Please provide a valid email address	no TLD
a@b.c	No error	Please provide a valid email address	TLD less than two characters

No changes in the rest of other invalid emails:

Invalid email	Same behaviour before and after	Reason
"A"@b.co	Please provide a valid email address	quoted emails
ab.co	Please provide a valid email address	no @ symbol
a@b@c.co	Please provide a valid email address	several @ symbol
a@-b.co	Please provide a valid email address	domain starting with hyphen
a@b-.co	Please provide a valid email address	domain finishing with hyphen
a@example_me.co	Please provide a valid email address	domain with underscore
a@[123.123.123.123]	Please provide a valid email address	IP addresses

Closes #499244 (closed)

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Before	After

Screenshots or screen recordings

1. Go to either:

• /users/sign_up or
• /-/trial_registrations/new (SAAS enabled)

1. Check the email field in the registration

Related to #499244 (closed)

app/assets/javascripts/pages/sessions/new/email_format_validator.js

 import InputValidator from '~/validators/input_validator';
 
-// It checks if email contains at least one character, number or whatever except
-// another "@" or whitespace before "@", at least two characters except
-// another "@" or whitespace after "@" and one dot in between
 const hintMessageSelector = '.validation-hint';
 
 export default class EmailFormatValidator extends InputValidator {