Use Fabric mixin in common classes

This is what both Fabric and NeoForge uses. This fixes the compilation
mismatch in DataFixersMixin — ModifyArg.at is now an array, so the
annotation data is slightly different. Annoyingly `javap -v` doesn't
show this, but asm's textifier does.

gradle/libs.versions.toml

@@ -11,7 +11,7 @@ fabric-api = "0.160.5+26.3"
 fabric-loader = "0.19.4"
 neoForge = "26.3.0.26-beta"
 neoMergeTool = "2.0.0"
-mixin = "0.8.5"
+mixin = "0.17.4+mixin.0.8.7"
 
 # Core dependencies (these versions are tied to the version Minecraft uses)
 fastutil = "8.5.18"
@@ -103,7 +103,7 @@ iris-forge = { module = "maven.modrinth:iris", version.ref = "iris-forge" }
 jei-api = { module = "mezz.jei:jei-26.3-common-api", version.ref = "jei" }
 jei-fabric = { module = "mezz.jei:jei-26.3-fabric", version.ref = "jei" }
 jei-forge = { module = "mezz.jei:jei-26.3-neoforge", version.ref = "jei" }
-mixin = { module = "org.spongepowered:mixin", version.ref = "mixin" }
+mixin = { module = "net.fabricmc:sponge-mixin", version.ref = "mixin" }
 mixinExtra = { module = "io.github.llamalad7:mixinextras-common", version.ref = "mixinExtra" }
 modmenu = { module = "com.terraformersmc:modmenu", version.ref = "modmenu" }
 rei-api = { module = "me.shedaniel:RoughlyEnoughItems-api", version.ref = "rei" }

projects/common/build.gradle.kts

@@ -41,15 +41,6 @@ sourceSets.testFixtures {
     compileClasspath += sourceSets.main.get().compileClasspath + sourceSets.client.get().compileClasspath
 }
 
-repositories {
-    exclusiveContent {
-        forRepositories(maven("https://maven.neoforged.net/releases"))
-        filter {
-            includeModule("org.spongepowered", "mixin")
-        }
-    }
-}
-
 dependencies {
     // Pull in our other projects. See comments in MinecraftConfigurations on this nastiness.
     api(project(":core"))

projects/fabric/build.gradle.kts

@@ -252,9 +252,6 @@ tasks.verifyClassesMatch {
     options.errorprone {
         option("ModLoader", "fabric")
     }
-
-    // For some reason we get a different class, despite the two files being the same.
-    ignoredFiles.add("dan200/computercraft/mixin/DataFixersMixin.class")
 }
 
 val runGametest = tasks.named<JavaExec>("runGametest") {

projects/forge/build.gradle.kts

@@ -246,9 +246,6 @@ tasks.verifyClassesMatch {
     options.errorprone {
         option("ModLoader", "forge")
     }
-
-    // For some reason we get a different class, despite the two files being the same.
-    ignoredFiles.add("dan200/computercraft/mixin/DataFixersMixin.class")
 }
 
 val runGametest = tasks.named<JavaExec>("runGametest") {