Added Anthem & Sydney as shared credentials

[ezfe]

Overall Checklist

• [x] I agree to the project's Developer Certificate of Origin
• [x] The top-level JSON objects are sorted alphabetically
• [x] There are no open pull requests for the same update

for shared-credentials.json

• [x] There's evidence the domains are currently related (SSL certificates, DNS entries, valid links between sites, legal documents etc.)

• https://www.sydneyhealth.com SSL certificate has alternate DNS entries for anthem.com domains

• Clicking "Read More" on https://www.sydneyhealth.com redirects to https://www.anthem.com/textprograms/

• https://membersecure.anthem.com/member/mobileapp (on anthem.com) describes the Sydney Health app

• [x] If using shared, the new group serves login pages on each of the included domains, and those login pages accept accounts from the others. (For example, we wouldn't use a shared association from google.co.il to google.com, because google.co.il redirects to accounts.google.com for sign in.)

• You can't sign in on https://www.sydneyhealth.com but the app for Sydney Health registers that domain so the iOS Password Manager doesn't suggest the anthem.com domains. Saving a password from that app saves it to sydneyhealth.com

[rmondello]

Looks good. Gotta fix up the merge conflict to land.

[ezfe]

Just resolved the merge conflict