Update core-ktx version (#6656)

Per [b/393388687](https://b.corp.google.com/issues/393388687),

This updates the `core-ktx` version to be `1.12.0` instead of `1.9.0`.
This version was accidentally downgraded in #6584.

Author: daymxn

gradle/libs.versions.toml

@@ -15,7 +15,7 @@ browser = "1.3.0"
 cardview = "1.0.0"
 checkerQual = "2.5.2"
 constraintlayout = "2.1.4"
-coreKtx = "1.9.0"
+coreKtx = "1.12.0"
 coroutines = "1.7.3"
 dagger = "2.43.2"
 dexmaker = "2.28.1"