Postpone showing You're earning tokens for viewing this sponsored image message till user connects to a custodian

[btlechowski]

Currently we are showing this message after enabling rewards and ads

Steps to Reproduce

1. Clean profile
2. Enable rewards and ads
3. Open NTP till NTP SI is shown
4. Connect to a custodian
5. Open NTP till NTP SI is shown

Actual result:

You're earning tokens for viewing this sponsored image message after enabling ads and rewards
You're earning tokens for viewing this sponsored image message is not shown after user connects to a custodian

Expected result:

You're earning tokens for viewing this sponsored image message is shown after user connects to a custodian

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

[LaurenWags]

Updated to QA/No as this will be verified with #28016.