Fix documentation for ImagenGenerationResponse (#6728)

Co-authored-by: David Motsonashvili <[email protected]>

Author: davidmotson

firebase-vertexai/src/main/kotlin/com/google/firebase/vertexai/type/ImagenGenerationResponse.kt

@@ -16,10 +16,11 @@
 
 package com.google.firebase.vertexai.type
 
+import com.google.firebase.vertexai.ImagenModel
 import kotlinx.serialization.Serializable
 
 /**
- * Represents a response from a call to [ImagenModel#generateImages]
+ * Represents a response from a call to [ImagenModel.generateImages]
  *
  * @param images contains the generated images
  * @param filteredReason if fewer images were generated than were requested, this field will contain