Make non-modal version actually work

[thatliuser]

There was quite a couple issues with the non-modal version merged in PR #11.

• There was a stray .call to a function that was originally wrapped by Modal, which has been removed.
• The file variable passed to main would cause the script would crash if a file wasn't passed.
• The filecode variable used to write the results of each file's code was improperly set as a tuple rather than a str, which would crash the script because there would be a type mismatch when calling write_file.

I've also removed a couple of miscellaneous things that aren't used anywhere:

• There was a retry variable that was not actually being considered when retrying.
• modal-client is a specified as a dependency in requirements.txt despite being a whole different way to run the app; if you use Modal, you shouldn't need requirements.txt at all since you install things through Modal!

[ShibbityShwab]

Just tested and this worked for me. Thank you!

[swyxio]

appreciate the fix!