Fixed WCAG issue with focusable TableRow

[framitdavid]

Description

There's no reason that TableRow should be focusable by tabIndex as default because the content within TableRow will automatically be focusable if they are interactive elements.

By removing the tabIndex we have the same tab-behaviour as material and bootstrap tables.

Related Issue(s)

• https://github.com/Altinn/app-frontend-react/issues/830

Verification

• [ ] Your code builds clean without any errors or warnings
• [x] Manual testing done (required)
• [x] Relevant automated test added (if you find this hard, leave it and we'll help out)
• [ ] All tests run green

Documentation

• [ ] User documentation is updated with a separate linked PR in altinn-studio-docs. (if applicable)