Add Site should probably read Add site in new-tab page's Favorites

Description

Add Site should probably read Add site in new-tab page’s Favorites

Steps to Reproduce

1. open the new-tab page
2. click Customize
3. choose Top Sites from the left
4. choose Favorites
5. dismiss the dialog
6. hover to the right of the Add site button
7. click on the ellipsis
8. note the capitalization of Add Site

Actual result:

It reads Add Site (upper-case)

Expected result:

Add site (lower-case)

Reproduces how often:

Brave version (brave://version info)

Brave	1.22.55 Chromium: 89.0.4389.72 (Official Build) beta (x86_64)
Revision	3f345f156bfd157bd1bea06310e55f3fb2490359-refs/branch-heads/4389@{#1393}
OS	macOS Version 11.2.3 (Build 20D91)

Version/Channel Information:

• Can you reproduce this issue with the current release? no
• Can you reproduce this issue with the beta channel? no
• Can you reproduce this issue with the nightly channel? yes

Other Additional Information:

• Does the issue resolve itself when disabling Brave Shields?
• Does the issue resolve itself when disabling Brave Rewards?
• Is the issue reproducible on the latest version of Chrome?

Miscellaneous Information:

[akshat-rawat]

@stephendonner, I have made the necessary changes and opened a PR for the same.

[stephendonner]

Verified FIXED using the inline testplan with build

Brave	1.28.54 Chromium: 92.0.4515.81 (Official Build) nightly (x86_64)
Revision	dba3af0a9a48954c8b188bc641e651580b7cb7b5-refs/branch-heads/4515@{#1162}
OS	macOS Version 11.4 (Build 20F71)

Steps:

1. open the new-tab page
2. click Customize
3. choose Top Sites from the left
4. choose Favorites
5. dismiss the dialog
6. hover to the right of the Add site button
7. click on the ellipsis ...

Confirmed it now reads Add site