Fix settings header for Snaps settings page in fullscreen

**What is this about?**

We show the wrong title in the settings header in full-screen mode

see: https://github.com/MetaMask/metamask-extension/pull/32151#discussion_r2056023068

**Stakeholder review needed before the work gets merged**

- [ ] Engineering (needed in most cases)
- [ ] Design
- [ ] Product
- [ ] QA (automation tests are required to pass before merging PRs but not all changes are covered by automation tests - please review if QA is needed beyond automation tests)
- [ ] Security
- [ ] Legal
- [ ] Marketing
- [ ] Management (please specify)
- [ ] Other (please specify)

Start by reviewing the linked pull request discussion and locating the Snaps settings page's fullscreen settings header. Confirm which title is currently shown and what title is expected; done means the correct title appears in fullscreen mode and the relevant checks pass.

Written by the indexing model from the issue text.