remove unneeded type heirarchy and update schema reference

Author: David Motsonashvili

firebase-ai/src/main/kotlin/com/google/firebase/ai/type/Schema.kt

@@ -412,14 +412,12 @@ internal constructor(
     )
   }
 
-  @Serializable internal sealed interface Internal
-
   @Serializable
   internal data class InternalOpenAPI(
     val type: String? = null,
     val description: String? = null,
     val format: String? = null,
-    val nullable: Boolean? = false,
+    val nullable: Boolean? = fals"e,
     val enum: List<String>? = null,
     val properties: Map<String, InternalOpenAPI>? = null,
     val required: List<String>? = null,
@@ -430,9 +428,9 @@ internal constructor(
     val minimum: Double? = null,
     val maximum: Double? = null,
     val anyOf: List<InternalOpenAPI>? = null,
-  ) : Internal
+  )
 
-  @Serializable internal sealed interface InternalJson : Internal
+  @Serializable internal sealed interface InternalJson
 
   @Serializable
   internal data class InternalJsonNonNull(

firebase-ai/update_responses.sh

@@ -17,7 +17,7 @@
 # This script replaces mock response files for Vertex AI unit tests with a fresh
 # clone of the shared repository of Vertex AI test data.
 
-RESPONSES_VERSION='v14.*' # The major version of mock responses to use
+RESPONSES_VERSION='v15.*' # The major version of mock responses to use
 REPO_NAME="vertexai-sdk-test-data"
 REPO_LINK="https://github.com/FirebaseExtended/$REPO_NAME.git"