Update regexp-matches-transact-sql.md

the match_value return column name was incorrectly named as string_expression

Author: hodgyhodson

docs/t-sql/functions/regexp-matches-transact-sql.md

@@ -56,7 +56,7 @@ Returns a tabular result as follows:
 | `match_id` | **bigint** | The sequence of matching words. |
 | `start_position` | **int** | Starting index position. |
 | `end_position` | **int** | Ending index position. |
-| `string_expression` | Same type as `string_expression` or **varchar** | Matching expression. |
+| `match_value` | Same type as `string_expression` or **varchar** | Matching expression. |
 | `substring_matches` | **json** | JSON document describing match. |
 
 ## Examples
@@ -89,4 +89,4 @@ match_id start_position end_position match_value substring_matches
 ## Related content
 
 - [Work with regular expressions](../../relational-databases/regular-expressions/overview.md)
-- [Regular expressions functions (Transact-SQL)](regular-expressions-functions-transact-sql.md)
+- [Regular expressions functions (Transact-SQL)](regular-expressions-functions-transact-sql.md)