Fix left overs from config struct

Author: daymxn

FirebaseAI/Sources/GenerativeModel.swift

@@ -89,7 +89,7 @@ public final class GenerativeModel: Sendable {
        systemInstruction: ModelContent? = nil,
        requestOptions: RequestOptions,
        urlSession: URLSession = GenAIURLSession.default,
-       useLimitedUseAppCheckTokens: Bool) {
+       useLimitedUseAppCheckTokens: Bool = false) {
     self.modelName = modelName
     self.modelResourceName = modelResourceName
     self.apiConfig = apiConfig

FirebaseAI/Sources/Types/Public/Imagen/ImagenModel.swift

@@ -54,7 +54,7 @@ public final class ImagenModel {
        safetySettings: ImagenSafetySettings?,
        requestOptions: RequestOptions,
        urlSession: URLSession = GenAIURLSession.default,
-       useLimitedUseAppCheckTokens: Bool) {
+       useLimitedUseAppCheckTokens: Bool = false) {
     self.modelResourceName = modelResourceName
     self.apiConfig = apiConfig
     generativeAIService = GenerativeAIService(

FirebaseAI/Tests/Unit/VertexComponentTests.swift

@@ -184,7 +184,7 @@ class VertexComponentTests: XCTestCase {
         app: app1,
         location: "transitory location",
         apiConfig: FirebaseAI.defaultVertexAIAPIConfig,
-        aiConfig: .config()
+        useLimitedUseAppCheckTokens: false
       )
       weakVertex = vertex
       XCTAssertNotNil(weakVertex)