fix(mixin): It's not static on 1.20.4

Author: null2264

cobblegen/src/main/java/io/github/null2264/cobblegen/mixin/network/loader/neoforge/NetworkRegistryMixin.java

@@ -19,7 +19,11 @@ public abstract class NetworkRegistryMixin {
         at = @At("HEAD"),
         cancellable = true
     )
-    private static void validateCobbleGenC2S(
+    private
+    #if MC>=12005
+    static
+    #endif
+    void validateCobbleGenC2S(
         net.minecraft.network.protocol.Packet<?> packet,
         net.minecraft.network.protocol.common.ServerCommonPacketListener listener,
         #if MC<12005
@@ -48,7 +52,11 @@ private static void validateCobbleGenC2S(
         at = @At("HEAD"),
         cancellable = true
     )
-    private static void validateCobbleGenS2C(
+    private
+    #if MC>=12005
+    static
+    #endif
+    void validateCobbleGenS2C(
         net.minecraft.network.protocol.Packet<?> packet,
         net.minecraft.network.protocol.common.ClientCommonPacketListener listener,
         #if MC<12005