schema has duplicate fields

## Expected Behavior 
feature_view.schema has no duplicate fields

## Current Behavior
feature_view.schema has no duplicate fields

## Steps to reproduce

### Specifications

- Version:
- Platform:
- Subsystem:

## Possible Solution

in feature_view:
```
    def schema(self) -> List[Field]:
        return list(set(self.entity_columns + self.features))
```
