Update README.md typo (#2132)

README.md

@@ -27,6 +27,6 @@ Acknowledgement
 ---------------
 We learnt a lot from the following projects when building TVM.
 - [Halide](https://github.com/halide/Halide): TVM uses [HalideIR](https://github.com/dmlc/HalideIR) as data structure for
-  arithematic simplification and low level lowering. We also learnt and adapted some part of lowering pipeline from Halide.
+  arithmetic simplification and low level lowering. We also learnt and adapted some part of lowering pipeline from Halide.
 - [Loopy](https://github.com/inducer/loopy): use of integer set analysis and its loop transformation primitives.
 - [Theano](https://github.com/Theano/Theano): the design inspiration of symbolic scan operator for recurrence.