upgrade foundry local core osx builds to use macos-15 (#611)

Co-authored-by: Prathik Rao <prathikrao@microsoft.com>

Author: prathikr

.pipelines/foundry-local-packaging.yml

@@ -192,7 +192,7 @@ extends:
         displayName: 'FLC osx-arm64'
         pool:
           name: Azure Pipelines
-          vmImage: 'macOS-14'
+          vmImage: 'macOS-15'
           os: macOS
         templateContext:
           outputs: