[tree view][docs] Adjust all demos height to account for the updated design

[danilo-leal]

• [x] I have followed (at least) the PR section of the contributing guide.

Closes https://github.com/mui/mui-x/issues/11976

Follow-up on the design update done on https://github.com/mui/mui-x/pull/11529 😃 I haven't added any overflow and rather just added fixed height for demos with a short amount of items and a min-height for those that have a bigger list.

[mui-bot]

Deploy preview: https://deploy-preview-11979--material-ui-x.netlify.app/

Generated by :no_entry_sign: dangerJS against 48e56cc4c6bfec0db98165b4468547e90e0603c6

[danilo-leal]

Uhm... the test_types check is picking up components I didn't even touch on this PR. 🤔 Any ideas why?

[flaviendelangle]

No idea, you can try to merge with next