Fix writing to read-only array bug in nerdss_converter.py

[PhysFoley]

This pull request fixes a small bug in the NERDSS converter that was causing it to fail due to attempting to write to a read-only numpy array.

Time estimate or Size

xsmall

Problem

NERDSS trajectories were failing to convert to simularium format due to an issue within the NerdssConverter class where it tried to write to elements of a read-only numpy array.

Solution

Create a copy of the numpy array with the same shape, edit this array, then overwrite the original.

Type of change

• Bug fix

Change summary:

• Fixed error "assignment destination is read-only" when calling NerdssConverter._read_pdb_files()

Steps to Verify:

1. Attempt to convert a NERDSS simulation using ionerdss.convert_simularium()

Keyfiles (delete if not relevant):

1. simulariumio/nerdss/nerdss_converter.py