Revert "Add toolchain configuration for buildSrc"

This reverts commit a28075a6a332f07ea9855ba4d5b18d8ea996b871.

buildSrc/build.gradle

@@ -5,11 +5,7 @@ plugins {
 	id 'com.apollographql.apollo' version '2.4.5'
 }
 
-java {
-	toolchain {
-		languageVersion = JavaLanguageVersion.of(17)
-	}
-}
+sourceCompatibility = JavaVersion.VERSION_17
 
 repositories {
 	gradlePluginPortal()