Exclude matplotlib 3.7 due to incompatible scanpy. (#929)

matplotlib just released v3.7, and unfortunately it introduced an
incompatibility with scanpy:

scverse/scanpy#2411

Excluding v3.7 works around this issue. This workaround can be removed
once scanpy itself excludes v3.7, or if scanpy fixes the root cause.

apis/python/setup.py

@@ -177,6 +177,7 @@ def run(self):
     install_requires=[
         "anndata",
         "attrs>=22.1",
+        "matplotlib<3.7",  # https://github.com/scverse/scanpy/issues/2411
         "numpy",
         "pandas",
         "pyarrow >= 9.0.0",