Restore title case for macOS menu items

[stephendonner]

Description

Restore title case for macOS menu items

NOTE: this is just for macOS - I'll be filing a separate bug for the Windows/Linux cases.

Steps to Reproduce

1. new profile
2. launch Brave
3. click on the "hamburger" menu
4. look carefully at the casing of the menu items

Actual result:

They are now a mix of sentence and title-case styles; see https://github.com/brave/brave-core/pull/8961/files#r674339383 which changed this.

Expected result:

Side by side (nightly vs. release)

nightly	release

Reproduces how often:

100%

Brave version (brave://version info)

Brave	1.29.45 Chromium: 92.0.4515.115 (Official Build) nightly (x86_64)
Revision	48cb2f4029b84b003719740a6cf9ca73f374a857-refs/branch-heads/4515_105@{#4}
OS	macOS Version 12.0 (Build 21A5294g)

/cc @bsclifton @wyatt400 @nullhook

[stephendonner]

Verified PASSED using

Brave	1.29.58 Chromium: 92.0.4515.131 (Official Build) beta (x86_64)
Revision	6b8d6c56ce21e38a72f7c4becb5abc1fa5134f29-refs/branch-heads/4515@{#1933}
OS	macOS Version 11.5.2 (Build 20G95)

Steps:

1. new profile
2. launched Brave
3. clicked on the "hamburger" menu and looked at the menu items' capitalizations/casing

Confirmed on macOS they are Sentence Case, correctly.

1.28.105	1.29.58