fix: Even more missing import

Author: null2264

1_21_9/src/neoforge/java/me/earth/mc_runtime_test/neoforge/mixin/GameTestHooksMixin.java

@@ -1,6 +1,7 @@
 package me.earth.mc_runtime_test.neoforge.mixin;
 
 import net.neoforged.neoforge.gametest.GameTestHooks;
+import org.spongepowered.asm.mixin.Mixin;
 import org.spongepowered.asm.mixin.injection.At;
 import org.spongepowered.asm.mixin.injection.Inject;
 import org.spongepowered.asm.mixin.injection.callback.CallbackInfoReturnable;