CLSA-2026-1790833998 libxml2: Fix of CVE-2026-74860

CVE-2026-74860: drop the extra PyDECREF on each enumeration value string in pythonAttributeDecl, since PyListSetItem already steals that reference...

CLSA-2026-1790786185 libxml2: Fix of CVE-2026-74860

CVE-2026-74860: drop the extra PyDECREF on each enumeration value string in pythonAttributeDecl, since PyListSetItem already steals that reference...