`Search the web privately` should read `Search the Web privately`, per our style guide

[stephendonner]

Description

Search the web privately should read Search the Web privately, per our style guide

Steps to reproduce

1. install 1.70.37
2. launch Brave
3. open a new-tab page
4. look at the prefilled text in the search textfield

Actual result

Search the web privately

Expected result

Search the Web privately

Reproduces how often

Easily reproduced

Brave version (brave://version info)

Brave | 1.70.37 Chromium: 127.0.6533.73 (Official Build) nightly (64-bit)
-- | --
Revision | 8556062edfbbe9023221ddaca3b6fe81264238c8
OS | Windows 10 Version 22H2 (Build 19045.4717)

Channel information

• release (stable)
• beta
• nightly

Reproducibility

• with Brave Shields disabled
• with Brave Rewards disabled
• in the latest version of Chrome

Miscellaneous information

cc @macauleyberg @rmcfadden3 @brave/qa-team @rebron