Closes https://github.com/zed-industries/zed/issues/51240

We don’t parse bsn as embedded Rust anymore. We expect bsn to get its
own Tree-sitter implementation in the future, which should improve this.
This fixes broken syntax highlighting for string literals. See line 66
in the comparison below.

<img width="2560" height="1440" alt="image"
src="https://github.com/user-attachments/assets/230ae057-f315-4290-8f51-bcd21e6557d7"
/>

Release Notes:

- N/A

Co-authored-by: Christopher Biscardi <chris@christopherbiscardi.com>