Fix typos in the SQL Roadmap (#5365)

Updated the row query definition. Row queries can return not just one but multiple rows.

src/data/roadmaps/sql/content/107-sub-queries/index.md

@@ -33,7 +33,7 @@ WHERE  column_name OPERATOR
    WHERE roll_id = (SELECT roll_id FROM student WHERE name='John');
    ```
 
-2. **Row subquery**: It returns single row of two or more values. 
+2. **Row subquery**: It returns a single row or multiple rows of two or more values. 
 
    ```sql
    SELECT * FROM student 
@@ -57,4 +57,4 @@ WHERE  column_name OPERATOR
 
 ## General Note
 
-Subqueries can be either correlated or uncorrelated. A correlated subquery is a subquery that uses values from the outer query. Conversely, an uncorrelated subquery is a subquery that can be run independently of the outer query.
+Subqueries can be either correlated or uncorrelated. A correlated subquery is a subquery that uses values from the outer query. Conversely, an uncorrelated subquery is a subquery that can be run independently of the outer query.