Update expat to 2.6.3 (#5185)

packages/e/expat/xmake.lua

@@ -4,6 +4,7 @@ package("expat")
     set_license("MIT")
 
     set_urls("https://github.com/libexpat/libexpat/releases/download/R_$(version).tar.bz2", {version = function (version) return version:gsub("%.", "_") .. "/expat-" .. version end})
+    add_versions("2.6.3", "b8baef92f328eebcf731f4d18103951c61fa8c8ec21d5ff4202fb6f2198aeb2d")
     add_versions("2.6.2", "9c7c1b5dcbc3c237c500a8fb1493e14d9582146dd9b42aa8d3ffb856a3b927e0")
     add_versions("2.5.0", "6f0e6e01f7b30025fa05c85fdad1e5d0ec7fd35d9f61b22f34998de11969ff67")
     add_versions("2.4.8", "a247a7f6bbb21cf2ca81ea4cbb916bfb9717ca523631675f99b3d4a5678dcd16")