Update Imagen 4 model version (#57)

Author: lethargicpanda

ai-catalog/samples/imagen/src/main/java/com/android/ai/samples/imagen/ImagenViewModel.kt

@@ -47,7 +47,7 @@ class ImagenViewModel @Inject constructor() : ViewModel() {
 
     @OptIn(PublicPreviewAPI::class)
     private val imagenModel = Firebase.ai(backend = GenerativeBackend.vertexAI()).imagenModel(
-        modelName = "imagen-4.0-generate-preview-05-20",
+        modelName = "imagen-4.0-generate-preview-06-06",
         generationConfig = ImagenGenerationConfig(
             numberOfImages = 1,
             aspectRatio = ImagenAspectRatio.SQUARE_1x1,

ai-catalog/samples/magic-selfie/src/main/java/com/android/ai/samples/magicselfie/MagicSelfieViewModel.kt

@@ -47,7 +47,7 @@ class MagicSelfieViewModel @Inject constructor() : ViewModel() {
     val progress: LiveData<String?> = _progress
 
     private val imagenModel = Firebase.ai(backend = GenerativeBackend.vertexAI()).imagenModel(
-        modelName = "imagen-4.0-generate-preview-05-20",
+        modelName = "imagen-4.0-generate-preview-06-06",
         generationConfig = ImagenGenerationConfig(
             numberOfImages = 1,
             aspectRatio = ImagenAspectRatio.PORTRAIT_3x4,