[Bug]: sp-table-head-cell with sortable cannot be activated by keyboard

### Code of conduct

- [X] I agree to follow this project's code of conduct.

### Impacted component(s)

sp-table-head-cell

### Expected behavior

Should be able to be sorted using the keyboard

### Actual behavior

neither space nor enter will sort the column

### Screenshots

_No response_

### What browsers are you seeing the problem in?

Firefox, Chrome, Safari, Microsoft Edge

### How can we reproduce this issue?

1. Go to https://opensource.adobe.com/spectrum-web-components/storybook/index.html?path=/story/table-virtualized--virtualized
2. Tab until you get to the sortable column title
3. Press enter
4. Nothing happens
5. Press space
6. page scrolls

### Sample code that illustrates the problem

_No response_

### Logs taken while reproducing problem

_No response_

Start with the sp-table-head-cell component and reproduce the issue in the linked Storybook table-virtualized example. Tab to a sortable column title, then test Enter and Space in the listed browsers. Done means both keys sort the column without scrolling the page.

Written by the indexing model from the issue text.