Replace tabs with spaces for non-Java files in this repo

I was looking at: https://github.com/GoogleCloudPlatform/spring-cloud-gcp/blob/main/spring-cloud-gcp-samples/spring-cloud-gcp-kotlin-samples/spring-cloud-gcp-kotlin-app-sample/src/main/kotlin/com/example/data/Person.kt

And noticed that the file uses tabs which isn't what's [recommended](https://developer.android.com/kotlin/style-guide).

Start with spring-cloud-gcp-samples/spring-cloud-gcp-kotlin-samples/spring-cloud-gcp-kotlin-app-sample/src/main/kotlin/com/example/data/Person.kt and compare its indentation with the linked Android Kotlin style guide. Search the repository's non-Java files for tabs, then replace the relevant indentation with spaces. Done means the targeted non-Java files no longer use tabs.

Written by the indexing model from the issue text.