[test] Update mock server for Swift 6 compliance #447

Job	Run time
Semantic Version label check	8s
musl	1m 29s
Unit tests / Construct unit test matrix	3s
Integration Tests / No dependencies on Foundation	1m 50s
Integration Tests / Test archive plugin	2m 11s
Integration Tests / Test Examples/APIGateway on 6.0.1-amazonlinux2	1m 23s
Soundness / API breakage check	1m 46s
Integration Tests / Test Examples/APIGateway+LambdaAuthorizer on 6.0.1-amazonlinux2	1m 21s
Integration Tests / Test Examples/BackgroundTasks on 6.0.1-amazonlinux2	1m 18s
Soundness / Broken symlinks check	3s
Integration Tests / Test Examples/HelloJSON on 6.0.1-amazonlinux2	1m 15s
Integration Tests / Test Examples/HelloWorld on 6.0.1-amazonlinux2	1m 13s
Soundness / Documentation check	1m 28s
Soundness / Format check	38s
Integration Tests / Test Examples/S3_AWSSDK on 6.0.1-amazonlinux2	4m 20s
Integration Tests / Test Examples/S3_Soto on 6.0.1-amazonlinux2	4m 55s
Soundness / License headers check	5s
Integration Tests / Test Examples/Streaming on 6.0.1-amazonlinux2	1m 17s
Soundness / Python lint check	7s
Integration Tests / Test Examples/Testing on 6.0.1-amazonlinux2	1m 26s
Integration Tests / Test Examples/Tutorial on 6.0.1-amazonlinux2	1m 17s
Soundness / Shell check	37s
Soundness / Unacceptable language check	2s
Soundness / YAML lint check	5s
Swift 6 Language Mode / Swift 6 language mode	1m 12s
Unit tests / Unit tests / Linux (6.0)	1m 22s
Unit tests / Unit tests / Linux (nightly-6.0)	1m 30s
Unit tests / Unit tests / Linux (nightly-main)	1m 27s
	35m 48s

Provide feedback