Update mac pipeline image variable (#48100)

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: danieljurek <2158838+danieljurek@users.noreply.github.com>

Author: Copilot

eng/pipelines/templates/variables/image.yml

@@ -15,7 +15,7 @@ variables:
   - name: WINDOWSVMIMAGE
     value: windows-2022
   - name: MACVMIMAGE
-    value: macos-latest
+    value: macos-15-arm64
 
   # Values required for pool.os field in 1es pipeline templates
   - name: LINUXOS
@@ -25,4 +25,3 @@ variables:
   - name: MACOS
     value: macOS
 
-