Fix gradle warning (#7956)

> Java toolchain auto-provisioning enabled, but no java toolchain
repositories declared by the build. Will rely on the built-in
repository. This behaviour has been deprecated and is scheduled to be
removed in Gradle 8.0. In order to declare a repository for java
toolchains, you must edit your settings script and add one via the
toolchainManagement block. See
https://docs.gradle.org/7.6.1/userguide/toolchains.html#sec:provisioning
for more details.

The sample at linked page mentions `repository("adoptium")` which looks
like what we would like to use, but apparently this is just a sample how
configuration might look like, `AdoptiumResolver` doesn't really exist.
The one that exists is https://github.com/gradle/foojay-toolchains

gradle-plugins/settings.gradle.kts

@@ -4,3 +4,7 @@ pluginManagement {
     id("io.github.gradle-nexus.publish-plugin") version "1.2.0"
   }
 }
+
+plugins {
+  id("org.gradle.toolchains.foojay-resolver-convention") version "0.4.0"
+}

settings.gradle.kts

@@ -15,6 +15,7 @@ pluginManagement {
 plugins {
   id("com.gradle.enterprise") version "3.12.2"
   id("com.gradle.common-custom-user-data-gradle-plugin") version "1.8.2"
+  id("org.gradle.toolchains.foojay-resolver-convention") version "0.4.0"
 }
 
 dependencyResolutionManagement {