Fix custom Brave Ad notifications should be attached to the browser window when repositioning ads on the screen

[btlechowski]

Follow up to #19464.

Steps to Reproduce

1. Clean install
2. Run Brave with: --enable-logging=stderr --vmodule="*/variations/*"=6,"*/bat-native-ledger/*"=6,"*/brave_rewards/*"=6,"*/bat-native-ads/*"=6,"*/bat-native-confirmations/*"=6,"*/brave_ads/*"=9,"*/brave_user_model/*"=6,"*/bat_ads/*"=6 --brave-ads-staging --rewards=staging=true --variations-server-url=https://v --enable-features="CustomAdNotifications:should_attached_ad_notification_to_browser_window/true"
3. Enable rewards and ads
4. Trigger a notification ad

Actual result:

Notification ad is attached to the screen when ad is moved rather than Brave Window

Note: Notice that the ad is cropped, this is logged under #22206

Expected result:

Notification ad is attached to Brave Window when ad is moved

Reproduces how often:

Easily reproduced

Brave version (brave://version info)

Brave	1.38.83 Chromium: 100.0.4896.79 (Official Build) beta (64-bit)
Revision	8fb749dcab8700c24213791969e59deb72fee36f-refs/branch-heads/4896@{#1015}
OS	Ubuntu 18.04 LTS

cc @brave/qa-team @jsecretan @tmancey @aseren

[aseren]

As I understand, a custom ad notification should have the same Z-order as a browser window. But should be attached to the edges of the screen.
So it seems like we have a wrong feature parameter naming here. It should be something like same_zorder_browser_window.
cc @tmancey

[tmancey]

Closed by #29744