[test] Update mock server for Swift 6 compliance #449

Job	Run time
Semantic Version label check	6s
musl	1m 30s
Unit tests / Construct unit test matrix	3s
Integration Tests / No dependencies on Foundation	1m 41s
Integration Tests / Test archive plugin	2m 17s
Integration Tests / Test Examples/APIGateway on 6.0.1-amazonlinux2	1m 26s
Swift 6 Language Mode / Swift 6 language mode	1m 9s
Integration Tests / Test Examples/APIGateway+LambdaAuthorizer on 6.0.1-amazonlinux2	1m 27s
Integration Tests / Test Examples/BackgroundTasks on 6.0.1-amazonlinux2	1m 16s
Soundness / API breakage check	1m 45s
Integration Tests / Test Examples/HelloJSON on 6.0.1-amazonlinux2	1m 20s
Soundness / Documentation check	1m 27s
Integration Tests / Test Examples/HelloWorld on 6.0.1-amazonlinux2	1m 15s
Integration Tests / Test Examples/S3_AWSSDK on 6.0.1-amazonlinux2	4m 18s
Soundness / License headers check	4s
Integration Tests / Test Examples/S3_Soto on 6.0.1-amazonlinux2	4m 43s
Soundness / Unacceptable language check	4s
Integration Tests / Test Examples/Streaming on 6.0.1-amazonlinux2	1m 16s
Soundness / Broken symlinks check	5s
Integration Tests / Test Examples/Testing on 6.0.1-amazonlinux2	1m 24s
Soundness / Format check	34s
Integration Tests / Test Examples/Tutorial on 6.0.1-amazonlinux2	1m 16s
Soundness / Python lint check	5s
Soundness / Shell check	30s
Soundness / YAML lint check	4s
Unit tests / Unit tests / Linux (6.0)	1m 21s
Unit tests / Unit tests / Linux (nightly-6.0)	1m 38s
Unit tests / Unit tests / Linux (nightly-main)	2m 27s
	36m 31s

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