Issue with finding NII.GZ files

The file that was given to me by @Mathilde-16 is called:
~~~
sub-MS0009_ses-20130224_cor_t1_3D_MPRAGE.nii.gz
~~~

However, this line of code looks for `*_T1w.nii.gz` file:
https://github.com/Mathilde-16/STOP_MS_data/blob/3857c957d9bdfeef6596b439bfa489f719cab94c/scripts/process_data.sh#L52

So that's not gonna work... 

Related to https://github.com/sct-pipeline/STOP-MS-data/issues/3