Bug 28679: Unable to click "Log in to your account" when GoogleOpenIDConnect is enabled

Bug 28679: Unable to click "Log in to your account" when GoogleOpenIDConnect is enabled

This patch corrects the login link in the OPAC when GoogleOpenIDConnect
is enabled. It removes modal-related markup which was causing the link
to fail.

To test, apply the patch and enable the GoogleOpenIDConnect system
preference.

- In the OPAC, click the "Log in to your account" link in the header.
  You should be redirected to a Google authentication form.
- Disable the GoogleOpenIDConnect preference. The login link in the OPAC
  should trigger a modal login form.

Signed-off-by: Lucas Gass <lucas@bywatersolutions.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>