Make getClocks OpenForTesting to test ClockCustomDemoFragment

Test: atest ClockRegistryTest ClockCustomDemoFragmentTest
Bug: 242332371
Change-Id: I1c300abf5b0b062c1657523475283a81bb6eed03

packages/SystemUI/shared/src/com/android/systemui/shared/clocks/ClockRegistry.kt

@@ -20,6 +20,7 @@ import android.net.Uri
 import android.os.Handler
 import android.provider.Settings
 import android.util.Log
+import androidx.annotation.OpenForTesting
 import com.android.internal.annotations.Keep
 import com.android.systemui.plugins.ClockController
 import com.android.systemui.plugins.ClockId
@@ -154,7 +155,8 @@ open class ClockRegistry(
         }
     }
 
-    fun getClocks(): List<ClockMetadata> {
+    @OpenForTesting
+    open fun getClocks(): List<ClockMetadata> {
         if (!isEnabled) {
             return listOf(availableClocks[DEFAULT_CLOCK_ID]!!.metadata)
         }