Revert "Update function"

Author: MikeRayMSFT

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

@@ -29,6 +29,15 @@ REGEXP_LIKE
      )
 ```
 
+> [!NOTE]
+> **REGEXP_LIKE** is available only under compatibility level 170 and above. If your database compatibility level is lower than 170, SQL Server can't find and run **REGEXP_LIKE**. Other regular expression scalar functions are available at all compatibility levels.
+>
+> You can check compatibility level in the `sys.databases` view or in database properties. You can change the compatibility level of a database with the following command:
+>
+> ```sql
+> ALTER DATABASE [DatabaseName] SET COMPATIBILITY_LEVEL = 170;
+> ```
+
 ## Arguments
 
 #### *string_expression*