[examples] Update APIGateway example with the new APIGatewayResponse initializer (#437)

After the merge of
awslabs/swift-aws-lambda-events#86
I updated the `APIGatewayV2Response` example to use the new initializer

Author: sebsto

Examples/APIGateway/Sources/main.swift

@@ -15,13 +15,6 @@
 import AWSLambdaEvents
 import AWSLambdaRuntime
 
-#if canImport(FoundationEssentials)
-import FoundationEssentials
-#else
-import Foundation
-#endif
-
-let encoder = JSONEncoder()
 let runtime = LambdaRuntime {
     (event: APIGatewayV2Request, context: LambdaContext) -> APIGatewayV2Response in
 
@@ -31,10 +24,7 @@ let runtime = LambdaRuntime {
     header["content-type"] = "application/json"
 
     // echo the request in the response
-    let data = try encoder.encode(event)
-    let response = String(decoding: data, as: Unicode.UTF8.self)
-
-    return APIGatewayV2Response(statusCode: .ok, headers: header, body: response)
+    return try APIGatewayV2Response(statusCode: .ok, headers: header, encodableBody: event)
 }
 
 try await runtime.run()