build(gradle): Upgrade Gradle

6.8 -> 8.8

server/build.gradle

@@ -1,40 +1,25 @@
-apply plugin: 'java'
-apply plugin: 'application'
-
-group = 'minecraft'
-version = '1.8.8'
-
-compileJava {
-    sourceCompatibility = targetCompatibility = 1.8
-    options.encoding = 'UTF-8'
-}
+apply plugin: "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'
-}
-
-repositories {
-    mavenLocal()
-    mavenCentral()
-    flatDir { dirs '../libs' }
+    args "--nogui"
 }
 
 dependencies {
-    compile name: 'com/mojang/authlib/1.5.21/authlib-1.5.21'
+    implementation name: "com/mojang/authlib/1.5.21/authlib-1.5.21"
 
-    compile 'org.apache.commons:commons-lang3:3.3.2'
-    compile 'com.google.guava:guava:17.0'
-    compile 'org.apache.logging.log4j:log4j-core:2.0-beta9'
-    compile 'io.netty:netty-all:4.0.23.Final'
-    compile 'com.google.code.gson:gson:2.2.4'
-    compile 'commons-io:commons-io:2.4'
+    implementation "org.apache.commons:commons-lang3:3.3.2"
+    implementation "com.google.guava:guava:17.0"
+    implementation "org.apache.logging.log4j:log4j-core:2.0-beta9"
+    implementation "io.netty:netty-all:4.0.23.Final"
+    implementation "com.google.code.gson:gson:2.2.4"
+    implementation "commons-io:commons-io:2.4"
 }