Try using Xcode 26 for compiling against iOS 18

Author: peterfriese

.github/workflows/firebaseai.yml

@@ -26,8 +26,8 @@ jobs:
     strategy:
       matrix:
         include:
-          - os: macos-15
-            xcode: "16.4"
+          - os: macos-26
+            xcode: "26.0"
             platform: iOS
             device: iPhone 16 Pro
             ios_version: "18.6"