Update requirements-fmt.txt (#1001)

Reviewed By: xuzhao9

Differential Revision: D100852792

Author: jhou-jpg

python/requirements-fmt.txt

@@ -1,5 +1,5 @@
 # generated by `pyfmt --requirements`
-black==25.11.0
+black==26.3.1
 ruff-api==0.2.0
 stdlibs==2025.10.28
 ufmt==2.9.0