Fix default enrollment index copy, override for Agency cards

[thekaveman]

This is my fault for not catching in the review of #2047.

That PR changed the default copy on the enrollment/index.html page for the headline:

We found your record! Now let’s enroll your contactless card.

When that is only the headline for Agency Card enrollment flows.

The headline for every other flow should read:

Your eligibility is confirmed! You're almost there.

To Reproduce

Steps to reproduce the behavior:

1. Go to dev-benefits.calitp.org
2. Choose MST > CalFresh
3. Login with a senior Login.gov account
4. See error in enrollment index

Expected behavior

The default for enrollment index is as above.

Each agency card has their own template override for their specific headline.