Increase the minimum supported AGP version to 8.5+

Increase the minimum supported AGP version to 8.5+

DGP's current minimum supported AGP version is 7.4.2 

https://github.com/Kotlin/dokka/blob/v2.2.0-Beta/dokka-integration-tests/gradle/src/main/kotlin/org/jetbrains/dokka/it/gradle/junit/TestedVersionsSource.kt#L111

This will align DGP with KGP.
https://youtrack.jetbrains.com/issue/KT-84144/Bump-the-minimal-supported-AGP-version-to-8.5.2

