Update Brave Talk study to be in Release (staging)

[bsclifton]

No description provided.

[kjozwiak]

Verification PASSED on Win 10 x64 using the following build:

Brave | 1.28.104 Chromium: 92.0.4515.131 (Official Build) (64-bit)
--- | ---
Revision | 6b8d6c56ce21e38a72f7c4becb5abc1fa5134f29-refs/branch-heads/4515@{#1933}
OS | Windows 10 OS Version 2009 (Build 19042.1151)

• ensured that Brave Talk widget was enabled via NTP on main (staging) after launching via the following:

--variations-server-url=https://variations.bravesoftware.com/seed

• ensured that BraveTalkStudy as enabled via brave://version/?show-variations-cmd
• moved the date ahead by three days and ensured that the popup/on-boarding appeared via the NTP

Widget Enabled	On-boarding under NTP