change pytato branch

Author: majosm

requirements.txt

@@ -6,4 +6,4 @@ git+https://github.com/inducer/pyopencl.git#egg=pyopencl
 git+https://github.com/inducer/islpy.git#egg=islpy
 
 git+https://github.com/inducer/loopy.git#egg=loopy
-git+https://github.com/inducer/pytato.git#egg=pytato
+git+https://github.com/majosm/pytato.git@sparse-matrix#egg=pytato