Upgrade Kotlin to 1.8.20 (#4753)

Summary:
[android] Upgrade Kotlin to 1.8.20
The additional source/target settings should hopefully no longer be necessary with
AGP 8.1:

https://kotlinlang.org/docs/gradle-configure-project.html#gradle-java-toolchains-support

Pull Request resolved: https://github.com/facebook/flipper/pull/4753

Test Plan:
- CI
- Build sample app
- AS sync

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Stack created with [Sapling](https://sapling-scm.com). Best reviewed with [ReviewStack](https://reviewstack.dev/facebook/flipper/pull/4753).
* https://github.com/facebook/flipper/issues/4759
* https://github.com/facebook/flipper/issues/4758
* https://github.com/facebook/flipper/issues/4757
* https://github.com/facebook/flipper/issues/4756
* https://github.com/facebook/flipper/issues/4755
* https://github.com/facebook/flipper/issues/4754
* __->__ https://github.com/facebook/flipper/issues/4753
* https://github.com/facebook/flipper/issues/4752
* https://github.com/facebook/flipper/issues/4751

Reviewed By: ivanmisuno

Differential Revision: D46068906

Pulled By: passy

fbshipit-source-id: 93da60ebfe2ec590ef88ea1936fcfd5257699cc7

gradle.properties

@@ -19,7 +19,7 @@ POM_ISSUES_URL=https://github.com/facebook/flipper/issues/
 # Shared version numbers
 LITHO_VERSION=0.44.0
 ANDROIDX_VERSION=1.3.0
-KOTLIN_VERSION=1.6.20
+KOTLIN_VERSION=1.8.20
 FBJNI_VERSION=0.3.0
 SOLOADER_VERSION=0.10.4
 # NDK