style(tree-grid): set content-box explicitly to avoind bootstrap override

[dkamburov]

Closes #273199

Additional information (check all that apply):

• [ ] Bug fix
• [ ] New functionality
• [ ] Documentation
• [ ] Demos
• [ ] CI/CD

Checklist:

• [ ] All relevant tags have been applied to this PR
• [ ] This PR includes unit tests covering all the new code
• [ ] This PR includes API docs for newly added methods/properties
• [ ] This PR includes general feature table updates in the root README.MD
• [ ] This PR contains breaking changes
• [ ] This PR includes behavioral changes and the feature specification has been updated with them