Change http to https for Grande Prairie proxy prefix

[ghost]

Describe the bug
In the YAML config file that contains the NEOS libraries' proxy prefixes, the GPRC proxy is http rather than htttps. This is causing error with links from the NEOS catalogue to individual vendor records.

To Reproduce
Steps to reproduce the behavior:

1. Go to https://catalogue.neoslibraries.ca/catalog/7412319?lib=gp
2. URL for the GPRC link includes http version of the proxy prefix
   We can't reproduce the problem (because we don't have GPRC proxy credentials) but GPRC has sent us a screenshot of the security error received when the link is followed (see below).

Expected behavior
Users should pass from the NEOS catalogue to the vendor page through the proxy without a security error.

Screenshots

Additional context
This information is stored here:

NEOSDiscovery/db/migrate/202002/library.yml

Line 36 in 65e6c96

proxy: "http://agpc.talonline.ca/login?url="

I don't know if we're still using this YAML file for the information. I won't make the change to this file since I'm not 100% this is where this info still lives.

If necessary, we can ask Anne Carr-Wiggin or the NEOS Discovery Subcommittee to re-verify this information, but this is the only problem report we've received.