Removed Java 8 target

Author: Anuken

build.gradle

@@ -33,15 +33,6 @@ ext{
     sdkRoot = System.getenv("ANDROID_HOME") ?: System.getenv("ANDROID_SDK_ROOT")
 }
 
-//java 8 backwards compatibility flag
-allprojects{
-    tasks.withType(JavaCompile).tap{
-        configureEach{
-            options.compilerArgs.addAll(['--release', '8'])
-        }
-    }
-}
-
 dependencies{
     def useLatest = false //set to "true" to always depend on the newest version of mindustry