[Maccore] Bump to the latest main. (#18799)

Bump maccore to bring the changes for governance and some others.

New commits in xamarin/maccore:

* xamarin/maccore@63fd14954c [Governance] Update the false positives
files based on the last runs.
* xamarin/maccore@b1c091dbb3 [certificates] Update la_dev_apple.p12,
la_distr_apple.p12 and la_mac_installer_distr.p12
* xamarin/maccore@cf71695c0b [mlaunch] Refactor project structure
* xamarin/maccore@3a0953b2a9 [XmlDocSync] Remove the XmlDocSync
reference from the project.
* xamarin/maccore@f243acfe79 [Submission] Add NotaryTool Task
* xamarin/maccore@ec9db0a40e Merge 'xcode15' into 'main'.
* xamarin/maccore@dc38700a6d [Governance] Update false positives take 2.

Diff:
fd15821e67...dc38700a6d

---------

Co-authored-by: Rolf Bjarne Kvinge <rolf@xamarin.com>

mk/xamarin.mk

@@ -7,7 +7,7 @@ MONO_BRANCH    := $(shell cd $(MONO_PATH) 2> /dev/null && git symbolic-ref --sho
 endif
 
 ifdef ENABLE_XAMARIN
-NEEDED_MACCORE_VERSION := fd15821e6780a7439df467c69eb511a046adfa06
+NEEDED_MACCORE_VERSION := 48e39158bd4730d5426fcb3ab570903161580e15
 NEEDED_MACCORE_BRANCH := main
 
 MACCORE_DIRECTORY := maccore