Unnecessary period in string for Show sidebar in Polish locale

[btlechowski]

Just delete that period

Steps to Reproduce

1. Run Brave in Polish PL locale
2. Open Hamburger menu
3. Check Show sidebar

Actual result:

Pokaż boczny pasek. (note the period in the end of the sentence)

Expected result:

Pokaż boczny pasek

Reproduces how often:

Easily reproduced

Brave version (brave://version info)

Brave	1.37.107 Chromium: 100.0.4896.46 (Official Build) (64-bit)
Revision	5ca33821b2211805855c77d334353d27c616a7ca-refs/branch-heads/4896@{#584}
OS	Ubuntu 18.04 LTS

cc @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