remove isCorrectModality function and its call in quicktest

[rwblair]

Quicktest looks to see if there was at least one file that either:

1. had a .nii extension and was in a either a func, anat, or dwi directory
2. had a json or tsv extension and was in any other accepted modality directory.

This is causing more problems that it solves:
https://neurostars.org/t/quick-validation-failed-on-physiological-files/17611

We now have regex to let users know what is a correctly or incorrectly formed filename. This PR makes quicktest just test that at least one subject session directory exists.

[effigies]

Sorry, I maybe should have blocked this. I thought we'd decided it was appropriate to require at least one NIfTI file in func/?

[rwblair]

We did, merging it was premature. I woke up this morning and the isCorrectModality code rubbed me the wrong way so I hit merge. It should be replaced at some point, guess it would be good to make a json/yaml way of denoting required files.

I'll revert and expand the quick validation error message to make it more transparent what exactly its looking for.