Address the following Deprecation warning

[biffgaut]

PASS test/test.apigateway-iot.test.js (7.958 s)
✓ Test for default Params construct props (126 ms)
✓ Test for default IAM Role (254 ms)
✓ Test for default Params request validator (144 ms)
✓ Test for default Params Integ Props and Method Props (128 ms)
✓ Test for valid iot enpoint (5 ms)
✓ Test for Binary Media types (126 ms)
✓ Test for Api Name and Desc (104 ms)
✓ Test for overriden IAM Role (103 ms)
✓ Test for APi Key Source (94 ms)
✓ Test for Api Key Creation (314 ms)
✓ Test for deployment ApiGateway AuthorizationType override (92 ms)
✓ Test for deployment ApiGateway AuthorizationType override (81 ms)
✓ Test for handling fully qualified iotEndpoint (138 ms)

console.warn
[WARNING] @aws-cdk/aws-apigateway.UsagePlanProps#apiKey is deprecated.
use addApiKey()
This API will be removed in the next majo

Also found in aws-cloudfront-apigateway-lambda