Remove `showHalo` from `AvatarToken` and `AvatarNetwork` components

### What is this about?

Remove the `showHalo` property from the `AvatarToken` and `AvatarNetwork` components, as it is no longer a required style for the Avatar components. All relevant styles and documentation should be updated, and an audit should be performed to ensure no Avatars are using the `showHalo` prop.

### Scenario

_No response_

### Design

_No response_

### Technical Details

- Remove the `showHalo` prop from the `AvatarToken` and `AvatarNetwork` component implementations.
- Update any stylesheets or inline styles that reference `showHalo`.
- Modify related tests to remove references to `showHalo`.
- Update component documentation to reflect the removal of `showHalo`.
- Perform an audit across the codebase to ensure no instances of `showHalo` remain.

### Threat Modeling Framework

_No response_

### Acceptance Criteria

- The `showHalo` prop is fully removed from the `AvatarToken` and `AvatarNetwork` components.
- All related styles are updated to exclude `showHalo`.
- Tests are updated and passing.
- Documentation is updated to reflect these changes.
- No instances of `showHalo` are found in the codebase after an audit.

### Stakeholder review needed before the work gets merged

- [X] 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

- [Slack thread](https://consensys.slack.com/archives/C0354T27M5M/p1721690421688269?thread_ts=1721672855.815649&cid=C0354T27M5M)
- [Figma thread](https://www.figma.com/design/bC6RgeriyERMtMlZE8xwkm?node-id=1341-39230#884530765)

Start by searching the codebase for `showHalo` and locating the `AvatarToken` and `AvatarNetwork` implementations, related styles, tests, and component documentation. Remove the prop and its references across those areas, update the tests and documentation, then repeat the search and run the relevant test suite to confirm no instances remain.

Written by the indexing model from the issue text.