depreciation warnings

[JessieGould]

• " AiidaDeprecationWarning: chdir() is deprecated and will be removed in the next major version. Use absolute paths instead. (this will be removed in v3) "
• "AiidaDeprecationWarning: parse_xml_post_6_2() is deprecated. Use parse_xml() instead which takes a file-like object. This function will be removed in aiida-quantumespresso v5.0."
• "legacy.py:18: AiidaDeprecationWarning:"

As seen when running examples/tutorials/workgraphs/md_workgraph.ipynb