fix: fix dependency issue in fastavro (#241)

* fixing dependency version to last version that supports Python 2.7

* Update noxfile.py

Removing fastavro dependency.

Co-authored-by: Tim Swast <swast@google.com>

Co-authored-by: Tim Swast <swast@google.com>

noxfile.py

@@ -92,7 +92,6 @@ def system(session):
     # Install all test dependencies, then install local packages in place.
     session.install("mock", "pytest", "psutil", "google-cloud-testutils")
     session.install("google-cloud-storage")
-    session.install("fastavro")
     session.install("-e", ".[all]")
 
     # IPython does not support Python 2 after version 5.x