Revert "Pin JDK release for AbstractCompile on 8"

This reverts commit 09dab0a.

Author: Goooler

build.gradle.kts

@@ -15,6 +15,11 @@ version = providers.gradleProperty("VERSION_NAME").get()
 group = providers.gradleProperty("GROUP").get()
 description = providers.gradleProperty("POM_DESCRIPTION").get()
 
+java {
+  sourceCompatibility = JavaVersion.VERSION_1_8
+  targetCompatibility = JavaVersion.VERSION_1_8
+}
+
 gradlePlugin {
   website = providers.gradleProperty("POM_URL")
   vcsUrl = providers.gradleProperty("POM_URL")
@@ -88,14 +93,6 @@ dependencies {
   testImplementation("org.junit.platform:junit-platform-suite-engine")
 }
 
-tasks.withType<GroovyCompile>().configureEach {
-  options.release = 8
-}
-
-tasks.withType<JavaCompile>().configureEach {
-  options.release = 8
-}
-
 tasks.withType<Test>().configureEach {
   useJUnitPlatform()