Niggling redundant MDAnalysis warnings in polyconf

[recombinatrix]

MDAnalysis generates warnings when importing monomer PDB files that lack information on formal charges or chainIDs

These datatypes are not used or required by polyconf

For example, see what happens when you execute polyconf_examples/02a_build_PMMA_isotactic.py

ada@Arbit ~/g/r/p/polyconf_examples (documentation_20250217)> python 02a_build_PMMA_isotactic.py
creating an isotactic PMMA polymer
/opt/homebrew/Caskroom/miniforge/base/envs/polyconf-dev/lib/python3.10/site-packages/MDAnalysis/coordinates/PDB.py:1154: UserWarning: Found no information for attr: 'formalcharges' Using default value of '0'
  warnings.warn("Found no information for attr: '{}'"
/opt/homebrew/Caskroom/miniforge/base/envs/polyconf-dev/lib/python3.10/site-packages/MDAnalysis/coordinates/PDB.py:1201: UserWarning: Found missing chainIDs. Corresponding atoms will use value of 'X'
  warnings.warn("Found missing chainIDs."

Luna, if you have time, would you be able to investigate whether you can silence these warnings?

[lunamorrow]

On it! Initial study shows that the warnings are being propagated when PDB._write is called, which is calling the MDAnalysis AtomGroup 'write()' method. I'll figure out how to suppress these warnings if possible.

[lunamorrow]

Resolved in #73