[Python][Parquet] element_type is nullable despite being non-null

### Describe the bug, including details regarding any error messages, version, and platform.

I have a column where each element is an array of floats (vector embeddings). Those floats are never null. I need to persist this column in this exact format but pyarrow will always set the inner element_type to `optional`. FastParquet seems to have an option `has_nulls=False` for similar purposes but FastParquet does not seem to be able to write nested array types at all.

This is the pyarrow schema type of the column:
```
('embedding', pyarrow.list_(pyarrow.float32(), list_size=1024, False),
```
And this is the resulting parquet schema
```
required group field_id=-1 embedding (List) {
repeated group field_id=-1 list {
optional float field_id=-1 element;
}
}
```

No matter what I try, I don't find a way to set the `optional` qualifier of the inner element to `required`. For my purposes, I need this exact schema and it seems problematic that pyarrow cannot create it despite the pyarrow documentation explicitly acknowledging that the inner element type may be either `required` or `optional`.

### Component(s)

Python