F-string formatting: Instable formatting for tuple with trailing comma

```py
print(f"{ {}, 1, }")
```

Gets formatted to 

```py
print(
    f"{ {}, 1 }"
)

```

notice that the trailing comma is missing but `print` expands because of the trailing comma's `expand_parent`.

Which then get formatted to 

```py
print(f"{ {}, 1 }")
```