Update codeowners to SwayEx (#803)

## Type of change

<!--Delete points that do not apply-->

- Improvement (refactoring, restructuring repository, cleaning tech
debt, ...)

## Changes

The following changes have been made:

- Application-dev team has been renamed to SwayEx. The codeowners file
now reflects it

## Checklist

- [ ] I have linked to any relevant issues.
- [ ] I have commented my code, particularly in hard-to-understand
areas.
- [ ] I have updated the documentation where relevant (API docs, the
reference, and the Sway book).
- [ ] If my change requires substantial documentation changes, I have
[requested support from the DevRel
team](https://github.com/FuelLabs/devrel-requests/issues/new/choose)
- [ ] I have added tests that prove my fix is effective or that my
feature works.
- [x] I have added (or requested a maintainer to add) the necessary
`Breaking*` or `New Feature` labels where relevant.
- [x] I have done my best to ensure that my PR adheres to [the Fuel Labs
Code Review
Standards](https://github.com/FuelLabs/rfcs/blob/master/text/code-standards/external-contributors.md).
- [x] I have requested a review from the relevant team or maintainers.

.github/CODEOWNERS

@@ -1 +1 @@
-* @FuelLabs/application-dev 
+* @FuelLabs/swayex