Update Pillow to 6.2.x

requirements/base.txt

@@ -2,4 +2,4 @@ Django>=2.2,<2.3
 django-dotenv==1.4.1
 wagtail>=2.6,<2.7
 wagtailfontawesome>=1.1.3,<1.2
-Pillow==4.0.0
+Pillow>=6.2.0,<6.3