Migrate nullability annotations to jSpecify

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

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

@@ -40,7 +40,7 @@ import net.minecraft.world.level.chunk.LevelChunk;
 import net.minecraft.world.phys.BlockHitResult;
 import net.minecraft.world.phys.Vec3;
 
-import javax.annotation.Nullable;
+import org.jspecify.annotations.Nullable;
 
 import static carpet.script.value.NBTSerializableValue.nameFromResource;