deps: support pyarrow 4 (#45)

Author: tswast

setup.py

@@ -45,7 +45,7 @@
         "ibis-framework >= 1.2.0,<3.0.0dev",
         "google-cloud-bigquery >=1.12.0,<3.0.0dev",
         "google-cloud-bigquery-storage >=1.0.0,<3.0.0dev",
-        "pyarrow >=1.0.0,<4.0.0dev",
+        "pyarrow >=1.0.0,<5.0.0dev",
         "pydata-google-auth",
     ],
     classifiers=[