Before the panel resize wouldn't take into account the width of the
sidebar and the right dock could push the left dock on resize too.

Before you mark this PR as ready for review, make sure that you have:
- [ ] Added a solid test coverage and/or screenshots from doing manual
testing
- [x] Done a self-review taking into account security and performance
aspects
- [x] Aligned any UI changes with the [UI
checklist](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)


Co-authored-by: Cameron \<cameron.studdstreet@gmail.com\>

Release Notes:

- N/A