[WelcomeUI] Update position of WDP on last screen

[rebron]

Description

Move the WDP row to the bottom and the check box should be unselected by default.

Steps to reproduce

1. Use 1.95.x.
2. Go to the final screen of brave://welcome-new
3. Last screen should have the WDP row on the bottom and unchecked.

Actual result

Expected result

Reproduces how often

Easily reproduced

Brave version (brave://version info)

1.95.x and higher

Channel information

• release (stable)
• beta
• nightly

Reproducibility

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

Miscellaneous information

No response