Yaml schema errors on FindInMap_Inside_Sub template

The schema appears to cause the below errors on https://github.com/awslabs/aws-cloudformation-templates/blob/master/aws/services/CloudFormation/FindInMap_Inside_Sub.yaml#L89-L91:
```
- {
87 # This is where we keep the complex things we want inserted into the Fn::Sub literal block
88 # You can even use Fn::If statements in this section
E 89 LocalFindInMapVarUsername: !FindInMap [ EnvMap, !Ref EnvNameParam, UserToCreate ], ■ unacceptable node kind for ! tag; it should be "scalar", not "sequence"
E 90 LocalFindInMapVarWebserver: !FindInMap [ EnvMap, !Ref EnvNameParam, WebServer ], ■■ unacceptable node kind for ! tag; it should be "scalar", not "sequence"
E 91 LocalIfVar: !If [ ExampleConditionIfDev, 'This box is development', 'This box is testing' ] ■■■ missed comma between flow collection entries
92 }
93 Outputs:
```

Use the referenced FindInMap_Inside_Sub.yaml template, especially lines 89–91, as the reproduction case. Inspect the schema validation for the flow-style Fn::FindInMap and Fn::If values, then rerun validation against the template; done means these reported schema errors no longer appear.

Written by the indexing model from the issue text.