chore: clean up pna25 feature flag

[ameliejyc]

Description

We no longer need the feature flag extensionUxPna25 which controlled the launch of the PNA25 toast message feature. This PR removes the feature flag code.

Changelog

CHANGELOG entry: null

Related issues

Fixes: https://consensyssoftware.atlassian.net/browse/CEUX-941

Manual testing steps

There is no change to the existing UX as now the feature is on by default. Some quick things that can be checked easily are:

• Verify onboarding metametrics string is correct:

• Verify PNA25 toast does not show for newly onboarded users
• Verify transaction_hash is included for PNA25 approved user transaction events

Screenshots/Recordings

Before

After

Pre-merge author checklist

• I've followed MetaMask Contributor Docs and MetaMask Mobile Coding Standards.
• I've completed the PR template to the best of my ability
• I've included tests if applicable
• I've documented my code using JSDoc format if applicable
• I've applied the right labels on the PR (see labeling guidelines). Not required for external contributors.

Pre-merge reviewer checklist

• I've manually tested the PR (e.g. pull and build branch, run the app, test code being changed).
• I confirm that this PR addresses all acceptance criteria described in the ticket it closes and includes the necessary testing evidence such as recordings and or screenshots.

---

Note

Medium Risk
Changes privacy/metrics gating logic by removing the extensionUxPna25 feature flag checks, which can affect when PNA25 acknowledgement is recorded and when transaction hashes are included in metrics.

Overview
Removes the extensionUxPna25 remote feature flag and all related selector/registry/mock code, simplifying PNA25 behavior to rely only on isPna25Acknowledged.

Updates onboarding and settings flows to always mark PNA25 as acknowledged on onboarding and when enabling MetaMetrics (if not already acknowledged), and updates metrics gating so ProfileMetricsController opt-in and transaction transaction_hash metrics depend solely on acknowledgement (no flag).

Refreshes copy and translations for the basic usage description, deletes flag-conditional UI rendering tests, and updates snapshots/smoke tests accordingly.

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🔍 Smart E2E Test Selection

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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
100.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[github-actions]

✅ E2E Fixture Validation — Schema is up to date
11 value mismatches detected (expected — fixture represents an existing user).
View details

[vinistevam]

✅ Confirmation