[KT-67559] Bumped the Xcode version to 15.3 in tested Xcode diagnostic

Author: IliaSolovei

native/utils/src/org/jetbrains/kotlin/konan/target/Xcode.kt

@@ -42,7 +42,7 @@ data class XcodeVersion(val major: Int, val minor: Int) : Comparable<XcodeVersio
             )
         }
 
-        val maxTested = XcodeVersion(15, 1)
+        val maxTested = XcodeVersion(15, 3)
     }
 }