amend audience for uid2 size to 0%

[dskamiotis]

What does this change?

Reduces the commercial-user-module-uid2 AB test audience size to 0% to enable opt-in only testing.

Why?

We're investigating why pbjs.getUserIds().uid2 returns undefined instead of a valid UID2 token as expected per The Trade Desk.

To debug this issue in production, we need to:

1. Test the UID2 module without the storage property (commercial#2335)
2. Limit exposure to opt-in users only (via ?ab-commercial-user-module-uid2=variant)
3. Validate token generation in the production environment

Setting audienceSize: 0% allows us to safely test the module configuration with real production data while controlling exactly who is exposed to the test via query parameters.

Testing

• Verify test can be activated via ?ab-commercial-user-module-uid2=variant
• Confirm pbjs.getUserIds().uid2 returns a valid token with the updated configuration
• Validate no users are automatically enrolled (0% audience)

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[Jakeii]

Ah this is a "holdback" test, so setting to 0% won't stop users getting this.

[dskamiotis]

Ah this is a "holdback" test, so setting to 0% won't stop users getting this.

Even with the changes to the commercial PR here?