fix: Change dbInstanceClass for postgres to small to be compatible with postgres 13.3 (#655)

Author: pgrzesik

aws-node-graphql-and-rds/resource/PostgreSqlRDSInstance.yml

@@ -5,10 +5,10 @@ Properties:
   MasterUserPassword: ${self:custom.PASSWORD}
   AllocatedStorage: 20
   DBName: ${self:custom.DB_NAME}
-  DBInstanceClass: db.t2.micro
+  DBInstanceClass: db.t4g.small
   VPCSecurityGroups:
   - !GetAtt ServerlessSecurityGroup.GroupId
   DBSubnetGroupName:
     Ref: ServerlessSubnetGroup
   Engine: postgres
-  PubliclyAccessible: true
+  PubliclyAccessible: true