Add exception for matplotlib license

(cherry picked from commit b3d867a)

Author: msimacek

mx.graalpython/mx_graalpython.py

@@ -2078,6 +2078,10 @@ def _python_checkpatchfiles():
             'tensorflow-io-gcs-filesystem-0.34.0.patch',
             # Whole license in the field. It's BSD-3-Clause
             'pyzmq.patch',
+            # Whole license in the field. It's PSF
+            'matplotlib-3.5.3.patch',
+            'matplotlib-3.6.3.patch',
+            'matplotlib-3.7.0.patch',
         }
         allowed_licenses = [
             "MIT",