BUG: Somato BIDS dataset derivatives need to be updated

Turns out there was a bug with the conversion in #6414 conversion. The subject used to be somato but now it’s 01 and the -src.fif was never updated. We thus end up with:

>>> fwd['src'][0]['subject_his_id']
'somato'

which is wrong (and is now arguably correctly treated as an error downstream later by MNE). I have a quick fix for this but it would be good @jasmainak @sappelhoff if someone could re-create the src, fwd, and (if applicable) inv for this subject because they will all have the old, incorrect subject_his_id value.

[larsoner]

No I would not create a new one, just use read_forward_solution, modify s['subject_his_id'] for each s in fwd['src'], then write_forward_solution. It ensures that everything stays the same except the subject_his_id

[sappelhoff]

@larsoner to create a new (correct) one, I assume that I would use mne.make_forward_solution

What should I supply for the src and bem parameters?

These are all the files I have (printed up to depth 3):

|MNE-somato-data/
|--- subjects/
|------ somato/
|--------- scripts/
|--------- stats/
|--------- label/
|--------- touch/
|--------- surf/
|--------- mri/
|--------- trash/
|--------- tmp/
|--------- src/
|--------- bem/
|--- MEG/
|------ somato/
|--------- sef_raw_sss-trans.fif
|--------- somato-meg-oct-6-fwd.fif
|--------- sef_raw_sss.fif