Make grandfather unverified similar to unconnected state for ads

[btlechowski]

After upgrade to 1.48.x aka grandfather unverified, we shouldn't show ads stats at all as they does not matter, instead we should show message similar to unconnected state cc @tmancey

Steps to Reproduce

1. Install 1.47.x
2. Clean profile
3. Enable rewards and ads
4. Upgrade to 1.48.x
5. Open brave://rewards

Actual result:

We do not immediately offer solution to the problem aka connect to custodian.
We ask users to click Learn More to find the solution in wall of text.
Misleading users as it says that user will earn BAT by viewing ads in this state

Expected result:

Show message urging users to connect to a custodian, similar to unconnected state shown below.
Also include link to https://brave.com/rewards-changes, explaining the changes to existing users.

Reproduces how often:

Easily reproduced

Brave version (brave://version info)

Brave	1.48.132 Chromium: 109.0.5414.87 (Official Build) beta (64-bit)
Revision	2dc18eb511c56e012081b4abc9e38c81c885f7d4-refs/branch-heads/5414@{#1241}
OS	Linux

cc @tmancey @Miyayes @LaurenWags