parser_.opts.python_decode_obj_api_strings doesn't apply for vector of strings

When a vector of strings is used, the generated code does not correctly decode into a string type and instead leaves the data as bytes (which is counter to the type hint).

Schema:

```
table test {
vec_of_string: [string];
single_string: string;
}

root_type test;
```
compiled with: `./build/flatc --python --python-version 3.12 --python-typing --gen-object-api
--python-decode-obj-api-strings -o /tmp/blah/ strings.fbs`

resulting code:

```python
class testT(object):

# testT
def __init__(self):
self.vecOfString = None # type: Optional[List[Optional[str]]]
self.singleString = None # type: Optional[str]
...
```

This is correct, though I would question if it shouldn't be `Optional[List[str]]` instead. (since the .pyi generates `typing.List[str]` not `str | None` like the single case)

```python
# testT
def _UnPack(self, test):
if test is None:
return
if not test.VecOfStringIsNone():
self.vecOfString = []
for i in range(test.VecOfStringLength()):
self.vecOfString.append(test.VecOfString(i))
self.singleString = test.SingleString()
if self.singleString is not None:
self.singleString = self.singleString.decode('utf-8')
```

This is incorrect. `self.vecOfString.append(test.VecOfString(i))` should be `self.vecOfString.append(test.VecOfString(i)).decode('utf-8')`. If it's actually optional, I guess it should do a None check first. But regardless it should be decoding to match the type hint.