build: Upgrade Gradle

6.8 -> 8.8

server/build.gradle

@@ -1,23 +1,15 @@
-apply plugin: 'java'
-apply plugin: 'application'
-
-group = 'minecraft'
-version = '1.2.5'
-
-compileJava {
-    sourceCompatibility = targetCompatibility = 1.8
-    options.encoding = 'UTF-8'
+plugins {
+    id "application"
 }
 
 application {
-    mainClassName = 'net.minecraft.server.MinecraftServer'
+    mainClassName = "net.minecraft.server.MinecraftServer"
 }
 
 run {
-    workingDir = new File(buildDir, 'run')
+    workingDir = new File(buildDir, "run")
     if (!workingDir.exists()) {
         workingDir.mkdir()
     }
-
-    args 'nogui'
+    args "nogui"
 }