Update GraalVM version to 23.1.8

Align to value here: https://github.com/micronaut-projects/micronaut-core/blob/4.10.x/gradle/libs.versions.toml#L13

Author: sdelamo

gradle.properties

@@ -46,7 +46,7 @@ developers=Graeme Rocher
 kotlin.stdlib.default.dependency=false
 
 # For the docs
-graalVersion=21.0.5
+graalVersion=23.1.8
 
 org.gradle.caching=true
 org.gradle.parallel=true