push.yml: build using macOS 26

Author: stephengold

.github/workflows/push.yml

@@ -102,7 +102,7 @@ jobs:
 
   Java21-MacOSX64:
     if: contains(toJson(github.event.commits), '[ci skip] ') == false
-    runs-on: macos-15-intel
+    runs-on: macos-26-intel
     steps:
       - uses: actions/setup-java@v5
         with:
@@ -132,7 +132,7 @@ jobs:
 
   Java21-MacOSX_ARM64:
     if: contains(toJson(github.event.commits), '[ci skip] ') == false
-    runs-on: macos-15
+    runs-on: macos-26
     steps:
       - uses: actions/setup-java@v5
         with: