chore(deps): update dependency pillow to v8 (GoogleCloudPlatform#4849)

Author: renovate-bot

appengine/flexible/scipy/requirements.txt

@@ -2,5 +2,5 @@ Flask==1.1.2
 gunicorn==20.0.4
 imageio==2.9.0
 numpy==1.19.2
-pillow==7.2.0
+pillow==8.0.0
 scipy==1.5.2