chore(deps): update dependency mypy to v0.812 (GoogleCloudPlatform#6034)

Author: renovate-bot

composer/workflows/constraints.txt

@@ -305,7 +305,7 @@ msrestazure==0.6.4
 multi-key-dict==2.0.3
 multidict==5.1.0
 mypy-extensions==0.4.3
-mypy==0.770
+mypy==0.812
 mysql-connector-python==8.0.25
 mysqlclient==1.3.14
 natsort==7.1.1