Remove extraneous @available check

Author: andrewheard

FirebaseVertexAI/Tests/TestApp/Tests/Integration/IntegrationTests.swift

@@ -19,7 +19,6 @@ import FirebaseVertexAI
 import VertexAITestApp
 import XCTest
 
-@available(iOS 15.0, macOS 12.0, macCatalyst 15.0, tvOS 15.0, watchOS 8.0, *)
 final class IntegrationTests: XCTestCase {
   // Set temperature, topP and topK to lowest allowed values to make responses more deterministic.
   let generationConfig = GenerationConfig(