Run on macos-15-arm64

Author: tgoyne

scripts/pr-ci-matrix.rb

@@ -82,7 +82,7 @@ def minimum_version(major)
     if not filter.call(version)
       next
     end
-    image = 'macos-15'
+    image = 'macos-15-arm64'
     output_file << """
   #{name}-#{version.gsub(' ', '_').gsub('.', '_')}:
     runs-on: #{image}