Update comments in read_nrml.py [skip CI]
Update comments in read_nrml.py [skip CI]

Following the change introduced in #5231, `noDamageLimit=None` is treated identical to `noDamageLimit=0`; modifying the code comments to reflect this change.
gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine