wendelin.core: v↑ 2.0.alpha3..post7 -> 2.0.alpha3.post9

wendelin.core 2.0.alpha3.post9 supports golang 1.21: with this new
version we can set golang 1.21 as the new default.

/reviewed-by @kirr and @jerome
/reviewed-on nexedi/slapos!1494

component/wendelin.core/buildout.cfg

@@ -50,7 +50,7 @@ CGO_LDFLAGS += -Wl,-rpath=${zlib:location}/lib
 recipe  = slapos.recipe.build:gitclone
 repository = https://lab.nexedi.com/nexedi/wendelin.core.git
 branch   = master
-revision = wendelin.core-2.0.alpha3-7-g885b355
+revision = wendelin.core-2.0.alpha3-9-gda765ef
 # dir is pretty name as top-level recipe
 location = ${buildout:parts-directory}/wendelin.core
 git-executable = ${git:location}/bin/git