gpui: Fix `shape_text` split to support \r\n (#31022)

Release Notes:

- N/A

---

Today I check the shape_text result on Windows, I get:

<img width="409" alt="屏幕截图 2025-05-20 222908"
src="https://github.com/user-attachments/assets/3ee93911-3de1-4e01-9433-00c626fc2369"
/>

Here the `shape_text` split logic I think it should use `lines` method,
not `split('\n')`, the newline on Windows is `\r\n`.
b7d5e6480aJason Lee committed on 5/20/2025, 2:53:50 PM· committed by GitHubparent0fa9f05
1 file changedLine totals unavailable