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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Screenshots or screen recordings

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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/views/devise/registrations/_signup_box_form.html.haml

@@ -64,7 +64,7 @@
         title: _('Please provide a valid email address.')
       %p.validation-hint.gl-field-hint.text-secondary
         = _('We recommend a work email address.')
-      %p.validation-warning.gl-field-error-ignore.text-secondary.hide
+      %p.validation-warning.gl-field-error-ignore.gl-text-red-500.hide
         = _('This email address does not look right, are you sure you typed it correctly?')
       -# This is used for providing entry to Jihu on email verification
       = render_if_exists 'devise/shared/signup_email_additional_info'