Pin breathe version due to incompatibility with sphinx >9 (#89)

### What change is being made

Pin breathe version.

### Why this change is being made

Fix `pixi run -e docs build`.

### Tested

`pixi run -e docs build` works now.

GitOrigin-RevId: 7be212439d21a80db1c9b59988986bf82c0596dc

Author: awoll-bdai

pixi.lock

@@ -135,7 +135,7 @@ sphinx = "*"
 furo = "*"
 sphinx-autodoc-typehints = "*"
 doxygen = "*"
-breathe = "*"
+breathe = ">=4.35.0"
 myst-parser = "*"
 
 [feature.docs.pypi-dependencies]