Some strings are not translated on ads earnings messages

[btlechowski]

Follow up to #17133

Steps to Reproduce

1. Run Brave in PL Polish locale
2. Get an ad grant
3. Check the messaging in Rewards settings page, NTP widget and BR panel

Actual result:

Some strings are not translated

Rewards settings page	NTP widget	BR panel

Expected result:

All strings are translated

Reproduces how often:

Easily reproduced

Brave version (brave://version info)

Verification passed on

Brave	1.37.101 Chromium: 99.0.4844.83 (Official Build) beta (64-bit)
Revision	b11086e62d7c1a44b0942ac5568d22a425c7ae35-refs/branch-heads/4844_74@{#5}
OS	Ubuntu 20 LTS

cc @brave/qa-team @rebron @mkarolin

[btlechowski]

Verification passed on

Brave	1.37.109 Chromium: 100.0.4896.60 (Official Build) beta (64-bit)
Revision	6a5d10861ce8de5fce22564658033b43cb7de047-refs/branch-heads/4896@{#875}
OS	Ubuntu 18.04 LTS

Verified test plan from the description