[CodesplainAppBar] Fix bug with selected org not being reset

[solkaz]

Description

Fixes issue with the selectedOrg not being reset to the user when creating a new snippet by dispatching an action to switch the selectedOrg value to the user's account

Motivation and Context

Fixes #529

Checklist:

• [x] My code follows the code style of this project.
• [x] I have added tests to cover my changes.
• [x] All new and existing tests passed.

Browsers

• [x] Chrome
• [x] Firefox
• [x] Safari
• [ ] Mobile:
• [ ] Other: