[DOCS] Fix typo in knn tuning guide (#113880) (#113922)

(cherry picked from commit 9b582c15ffc27e3ae3ce8961234b85966b2a8374)

docs/reference/how-to/knn-search.asciidoc

@@ -48,7 +48,7 @@ expensive to load. This could significantly slow down the speed of kNN search.
 NOTE: <<docs-reindex, reindex>>, <<docs-update, update>>,
 and <<docs-update-by-query, update by query>> operations generally
 require the `_source` field. Disabling `_source` for a field might result in
-expected behavior for these operations. For example, reindex might not actually
+unexpected behavior for these operations. For example, reindex might not actually
 contain the `dense_vector` field in the new index.
 
 You can disable storing `dense_vector` fields in the `_source` through the