Refactor Mixin build setup

common/addons/structure-sponge-loader/build.gradle.kts

@@ -2,10 +2,6 @@ import com.github.jengelman.gradle.plugins.shadow.tasks.ShadowJar
 
 version = version("1.0.0")
 
-repositories {
-    maven { url = uri("https://jitpack.io/") }
-}
-
 dependencies {
     api("commons-io:commons-io:2.7")
     api("com.github.Querz:NBT:6.1")