Release 5.21.2

This release contains a number of fixes with the interconversion
between markdown and html. As well as a number of bug fixes. This
release is primarily made, to support python 3.15.

What's Changed

• Allow building zlib and libsbml at the same time. by @luciansmith in #474
• Allow a model history parent to be set. by @luciansmith in #475
• Pull develop into branch by @luciansmith in #478
• Remove warnings by @luciansmith in #477
• Only call loadPlugins once in constructors. by @luciansmith in #469
• Use python 3.11 instead of 3.8 to build on manylinux by @fbergmann in #479
• Add main option to converters by @fbergmann in #480
• Fix memory leak in GeneProductAssociation::getFbcAssociationFor. by @luciansmith in #482
• log species reference with hOSU and initialConcentration as implicit reference by @fbergmann in #484
• Fix ASTNode's copyNode for constants. by @luciansmith in #485
• Fix table round-tripping. by @luciansmith in #486
• • bump version by @fbergmann in #487

Full Changelog: v5.21.1...v5.21.2