adding version checks

Author: srushtisv

FirebaseAuth/Sources/Swift/Backend/RPC/FinalizePasskeySignInRequest.swift

@@ -17,6 +17,7 @@
 /// The GCIP endpoint for finalizePasskeySignIn rpc
 private let finalizePasskeySignInEndPoint = "accounts/passkeySignIn:finalize"
 
+@available(iOS 15.0, macOS 12.0, tvOS 16.0, *)
 class FinalizePasskeySignInRequest: IdentityToolkitRequest, AuthRPCRequest {
   typealias Response = FinalizePasskeySignInResponse
   /// The credential ID

FirebaseAuth/Sources/Swift/Backend/RPC/FinalizePasskeySignInResponse.swift

@@ -14,6 +14,7 @@
  * limitations under the License.
  */
 
+@available(iOS 15.0, macOS 12.0, tvOS 16.0, *)
 struct FinalizePasskeySignInResponse: AuthRPCResponse {
   /// The user raw access token.
   let idToken: String