Bump maccore to get mlaunch fix.

New commits in xamarin/maccore:

* xamarin/maccore@0837e7caff [mlaunch] Load new libraries in Xcode 14.0

Diff: 713bcb2442..0837e7caff

mk/xamarin.mk

@@ -7,8 +7,8 @@ MONO_BRANCH    := $(shell cd $(MONO_PATH) 2> /dev/null && git symbolic-ref --sho
 endif
 
 ifdef ENABLE_XAMARIN
-NEEDED_MACCORE_VERSION := 713bcb2442ac70e1741f4dccd2afa5cfed546fdb
-NEEDED_MACCORE_BRANCH := main
+NEEDED_MACCORE_VERSION := 0837e7caffb2e42efcd183cb1d71998fb6022e2c
+NEEDED_MACCORE_BRANCH := xcode14
 
 MACCORE_DIRECTORY := maccore
 MACCORE_MODULE    := git@github.com:xamarin/maccore.git