Fix set api modal not submitting

[yamikaitou]

Description of the changes

Resolves the following traceback

Oct 12 02:40:54 bot python[64760]: [2025-10-12 02:40:54] [ERROR] discord.ui.modal: Ignoring exception in modal <SetApiModal timeout=None children=2>:
Oct 12 02:40:54 bot python[64760]: Traceback (most recent call last):
Oct 12 02:40:54 bot python[64760]:   File "/home/itazura/redenv/lib/python3.11/site-packages/discord/ui/modal.py", line 193, in _scheduled_task
Oct 12 02:40:54 bot python[64760]:     await self.on_submit(interaction)
Oct 12 02:40:54 bot python[64760]:   File "/home/itazura/redenv/lib/python3.11/site-packages/redbot/core/utils/views.py", line 445, in on_submit
Oct 12 02:40:54 bot python[64760]:     tokens = " ".join(self.token_input.value.split("\n")).rstrip()
Oct 12 02:40:54 bot python[64760]:                       ^^^^^^^^^^^^^^^^^^^^^^
Oct 12 02:40:54 bot python[64760]: AttributeError: 'Label' object has no attribute 'value'

Have the changes in this PR been tested?

Yes