`@encodedName` with same name of property emit error

While technically useless I am not sure this should be an error
```tsp
model Foo {
@encodedName("application/json", "foo")
foo: string;
}
```

```
error encoded-name-conflict Encoded name 'foo' conflicts with existing member name for mime type 'application/json'
```

[Playground Link](https://typespec.io/playground?c=bW9kZWwgRm9vIHsKICBAZW5jb2RlZE5hbWUoImFwcGxpY2F0aW9uL2pzb24iLCAiZm9vIikKICBmb286IHN0cmluZzsKfQ%3D%3D&e=%40typespec%2Fopenapi3&options=%7B%7D)