Fix bad template name

When a user register, the template displayed saying it should now check its email was misspelled.
Resulting in displaying the default one (with margin issue).

diff --git a/src/Wallabag/UserBundle/Resources/views/Registration/checkEmail.html.twig b/src/Wallabag/UserBundle/Resources/views/Registration/check_email.html.twig
similarity index 100%
rename from src/Wallabag/UserBundle/Resources/views/Registration/checkEmail.html.twig
rename to src/Wallabag/UserBundle/Resources/views/Registration/check_email.html.twig