fix: do not allow focusing of cell when not in cell selection mode

[Killusions]

What kind of change does this PR introduce? (check one with "x")

• [x] Bugfix
• [ ] Feature
• [ ] Code style update (formatting, local variables)
• [ ] Refactoring (no functional changes, no api changes)
• [ ] Build related changes
• [ ] CI related changes
• [ ] Other... Please describe:

What is the current behavior? (You can also link to an open issue here)

Currently, a cell can be focused by mouse, even when not in cell selectionMode, this creates an issue with focus styling and leads to the cell being selected by mouse instead of the row.

What is the new behavior?

Do not set tabindex=-1 on the cell if selectionMode is not cell, now clicking on a row focuses the entire row.

Does this PR introduce a breaking change? (check one with "x")

• [ ] Yes
• [x] No

If this PR contains a breaking change, please describe the impact and migration path for existing applications: ...

Other information: