Migrate nullability annotations to jSpecify

Mojang has done that, we don't need 3 different sets of annotations

src/main/java/carpet/script/value/EntityValue.java

@@ -80,7 +80,7 @@ import net.minecraft.world.phys.EntityHitResult;
 import net.minecraft.world.phys.HitResult;
 import net.minecraft.world.phys.Vec3;
 
-import javax.annotation.Nullable;
+import org.jspecify.annotations.Nullable;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.HashMap;