fix(android-setup): remove extra main elements in AndroidSetupSpinnerStep UIs

[dbjorge]

Description of changes

Several of the steps that are based on AndroidSetupSpinnerStep were wrapping it in a <main> element, but it already is based on AndroidSetupStepLayout which provides a <main> element. This removes the extra landmark.

No visual change.

Pull request checklist

• [n/a] Addresses an existing issue: #0000
• Ran yarn fastpass
• Added/updated relevant unit test(s) (and ran yarn test)
• Verified code coverage for the changes made. Check coverage report at: <rootDir>/test-results/unit/coverage
• PR title AND final merge commit title both start with a semantic tag (fix:, chore:, feat(feature-name):, refactor:). See CONTRIBUTING.md.
• [n/a] (UI changes only) Added screenshots/GIFs to description above
• (UI changes only) Verified usability with NVDA/JAWS