test: Add skip-smart-e2e-selection label for Feature Flag Drift CI (#28513)

## Description

Drift sync PRs are created by
`.github/workflows/check-feature-flag-registry-drift.yml` using the
reusable workflow `create-pr-feature-flag-registry-drift` from
`MetaMask/github-tools`.

This PR adds the `skip-smart-e2e-selection` label to the `pr-label`
input (in addition to `team-qa` and `no-changelog`) so automated
registry sync PRs can be excluded from smart E2E selection.

**Changed file:**
`.github/workflows/check-feature-flag-registry-drift.yml` (job
`create-drift-pr`).

## Changelog

CHANGELOG entry: null

## Related issues

Fixes: No ticket

## Manual testing steps

1. In GitHub Actions, open the workflow **Check Feature Flag Registry
Drift PROD**.
2. Confirm the `create-drift-pr` job passes `pr-label` including
`skip-smart-e2e-selection` (e.g. inspect a run that opens a drift PR, or
validate inputs against the reusable workflow docs).
3. On the opened drift PR, confirm labels include **team-qa**,
**no-changelog**, and **skip-smart-e2e-selection**.

## Screenshots / recordings

N/A — workflow-only change.

## Pre-merge author checklist

- [ ] I've followed [MetaMask Contributor
Docs](https://github.com/MetaMask/contributor-docs) and [MetaMask Mobile
Coding
Standards](https://github.com/MetaMask/metamask-mobile/blob/main/.github/guidelines/CODING_GUIDELINES.md).
- [ ] 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](https://jsdoc.app/) format
if applicable.
- [ ] I've applied the right labels on the PR per [labeling
guidelines](https://github.com/MetaMask/metamask-mobile/blob/main/.github/guidelines/LABELING_GUIDELINES.md).
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.

<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> **Low Risk**
> Low risk workflow-only change that only affects labels applied to
automated drift sync PRs; no runtime code paths or data handling are
modified.
> 
> **Overview**
> Automated feature-flag registry drift sync PRs created by
`check-feature-flag-registry-drift.yml` now include the
`skip-smart-e2e-selection` label in addition to the existing `team-qa`
and `no-changelog` labels, so these PRs can be excluded from smart E2E
test selection.
> 
> <sup>Reviewed by [Cursor Bugbot](https://cursor.com/bugbot) for commit
dca2238. Bugbot is set up for automated
code reviews on this repo. Configure
[here](https://www.cursor.com/dashboard/bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

Author: LeVinhGithub

.github/workflows/check-feature-flag-registry-drift.yml

@@ -82,7 +82,7 @@ jobs:
       report-artifact-name: drift-report
       workflow-run-url: https://github.com/${{ github.repository }}/actions/runs/${{ github.run_id }}
       pr-title-prefix: 'test: Sync Feature Flag Registry'
-      pr-label: 'team-qa,no-changelog'
+      pr-label: 'team-qa,no-changelog,skip-smart-e2e-selection'
     secrets:
       github-token: ${{ secrets.GITHUB_TOKEN }}