Remove dashes from estimated ads earnings in grandfathered unverified state

[btlechowski]

Not sure why they exist, just leave Learn More

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
6. Open NTP

Actual result:

dashes are shown next to Learn More

brave://rewards

NTP

Expected result:

dashes are not shown next to Learn More

brave://rewards

NTP

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