updated Pillow to fix vulnerability

Author: colin4554

requirements.txt

@@ -37,7 +37,7 @@ numpy==1.19.4
 oauth2client==3.0.0
 oauthlib==3.1.0
 pandas==1.1.5
-Pillow==8.1.0
+Pillow==8.1.1
 proto-plus==1.13.0
 protobuf==3.14.0
 psycopg2-binary==2.8.6