Remove unused parameter in `getCaip25PermissionFromLegacyPermissions`

### What is this about?

https://github.com/MetaMask/metamask-mobile/pull/15477 makes the `origin` parameter in `getCaip25PermissionFromLegacyPermissions` unnecessary. We should remove it and refactor its usage.

### Scenario

_No response_

### Design

_No response_

### Technical Details

_No response_

### Threat Modeling Framework

_No response_

### Acceptance Criteria

_No response_

### 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)

### References

_No response_

Locate getCaip25PermissionFromLegacyPermissions and inspect the changes introduced by pull request 15477. Remove the unnecessary origin parameter, update its usages, and run the relevant existing checks to confirm permission handling still works without it.

Written by the indexing model from the issue text.