Fix typo in the tutorials book

Author: Kriskras99

tutorials-book/src/SUMMARY.md

@@ -7,5 +7,5 @@
 - [Configuring ArrayFire Runtime Environment](./configuring_arrayfire_environment.md)
 - [Interoperability with CUDA](./cuda-interop.md)
 - [Interoperability with OpenCL](./opencl-interop.md)
-- [Multhi-Threading](./multi-threading.md)
+- [Multi-Threading](./multi-threading.md)
 - [Serialization & Deserialization](./serde.md)