Bug 21094: Syndetics: always use https instead of http

Bug 21094: Syndetics: always use https instead of http

This patch removes the 'using_https' check in OPAC templates in calls to
Syndetics resources. Instead, https is always used.

To test, apply the patch and enable Syndetics-related preferences. View
the following pages in the OPAC:

- Bibliographic detail page
  - Browse shelf section of the bibliographic detail page
- Search results
- List contents
- Recent comments
  - Recent comments RSS
- User summary page
  - Circulation history

NOTE: I tested with made-up Syndetics credentials. This means my changes
didn't make the template explode, but it doesn't confirm conclusively
that the resources work.

Signed-off-by: John Doe <you@example.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>