Bump marshmallow from 3.6.1 to 3.7.1 (#476)

dependabot[bot] · web-flow · commit 382b9f9925de · 2020-07-28T23:26:36.000+02:00
diff --git a/requirements/requirements.txt b/requirements/requirements.txt
@@ -1,5 +1,5 @@
 boto3~=1.14.10
-marshmallow==3.6.1
+marshmallow==3.7.1
 PyYAML>=5.1,<5.4
 requests==2.24.0
 cryptography==2.9.2
