Fix typo in math_verify package name

The real package path is https://pypi.org/project/math-verify. When I run `pipx install optillm` it does not install the `math-verify` package.

Author: theodorosploumis

requirements.txt

@@ -35,4 +35,4 @@ datasets
 mcp
 # MLX support for Apple Silicon optimization
 mlx-lm>=0.24.0; platform_machine=="arm64" and sys_platform=="darwin"
-math_verify
+math-verify