Do not use `permanent` when reading from cookies

[fredplante]

When we want to store a permanent cookies, we have to use the permanent accessor. When reading, this is not needed. See documentation :

This jar is only meant for writing. You'll read permanent cookies through the regular accessor.

When we want to check for a cookie existence, instead of doing:

cookies.encrypted[:remember_token].present?

we can do just:

cookies[:remember_token]

[fredplante]

@stevepolitodesign CI fixed in https://github.com/stevepolitodesign/rails-authentication-from-scratch/pull/92

You might want to merge the other first, then I'll rebase this one