Fix like_utf8 doctest

It was broken properly, with a bug in test, after commit c296882

Can drop this after rebase on commit e8cc39e "Fix like regex escaping (apache#1085)", first released in 7.0.0

Author: mcheshkov

arrow/src/compute/kernels/comparison.rs

@@ -217,7 +217,7 @@ where
 /// use arrow::compute::like_utf8;
 ///
 /// let strings = StringArray::from(vec!["Arrow", "Arrow", "Arrow", "Ar"]);
-/// let patterns = StringArray::from(vec!["A%", "B%", "A.", "A."]);
+/// let patterns = StringArray::from(vec!["A%", "B%", "A.", "A_"]);
 ///
 /// let result = like_utf8(&strings, &patterns).unwrap();
 /// assert_eq!(result, BooleanArray::from(vec![true, false, false, true]));