inline blame: Match icon size to font size in buffer (#11788)

This fixes #11311.


Release Notes:

- Fixed icon in inline git blame entry not changing with the buffer font
size. ([#11311](https://github.com/zed-industries/zed/issues/11311)).

Before:

![screenshot-2024-05-14-10 48
49@2x](https://github.com/zed-industries/zed/assets/1185253/4a288cae-a52b-4bee-8681-f1d9ba3b57f3)

After:

![screenshot-2024-05-14-10 50
06@2x](https://github.com/zed-industries/zed/assets/1185253/f7a6a608-8ecc-4642-adbd-80858dea75e9)
ec65035659Thorsten Ball committed on 5/14/2024, 9:06:16 AM· committed by GitHubparent9b74acc
2 files changedLine totals unavailable