Update iPhone 16 series iOS version in workflow

Author: finalerock44

.github/workflows/ios-devices-matrix.yml

@@ -43,9 +43,7 @@ jobs:
           - device: iphone-15
             ios-version: "17"
 
-          # iPhone 16 series (iOS 18, 26)
-          - device: iphone-16
-            ios-version: "18"
+          # iPhone 16 series (iOS 26)
           - device: iphone-16
             ios-version: "26"