Log Message:
expat: update to 2.4.6

Release 2.4.6 Sun February 20 2022
        Bug fixes:
            #566  Fix a regression introduced by the fix for CVE-2022-25313
                    in release 2.4.5 that affects applications that (1)
                    call function XML_SetElementDeclHandler and (2) are
                    parsing XML that contains nested element declarations
                    (e.g. "<!ELEMENT junk ((bar|foo|xyz+), \ 
zebra*)>").

        Other changes:
       #567 #568  Version info bumped from 9:5:8 to 9:6:8;
                    see https://verbump.de/ for what these numbers do