[mlir][sparse] fixed typo

Reviewed By: bixia

Differential Revision: https://reviews.llvm.org/D142784

Author: aartbik

mlir/lib/Dialect/SparseTensor/Transforms/SparseTensorStorageLayout.h

@@ -315,7 +315,7 @@ class SparseTensorDescriptorImpl {
   ValueArrayRef fields;
 };
 
-/// Uses ValueRange for immuatable descriptors;
+/// Uses ValueRange for immutable descriptors.
 class SparseTensorDescriptor : public SparseTensorDescriptorImpl<ValueRange> {
 public:
   SparseTensorDescriptor(Type tp, ValueRange buffers)