fix: format within_group error message (#16613)

Author: watchingthewheelsgo

datafusion/sql/src/expr/function.rs

@@ -228,7 +228,7 @@ impl<S: ContextProvider> SqlToRel<'_, S> {
         }
 
         if !order_by.is_empty() && !within_group.is_empty() {
-            return plan_err!("ORDER BY and WITHIN GROUP clauses cannot be used together in the same aggregate function. ");
+            return plan_err!("ORDER BY and WITHIN GROUP clauses cannot be used together in the same aggregate function");
         }
 
         // If function is a window function (it has an OVER clause),

datafusion/sqllogictest/test_files/aggregate.slt

@@ -7053,6 +7053,6 @@ FROM (VALUES ('a'), ('d'), ('c'), ('a')) t(a_varchar);
 ----
 [a, c, d]
 
-query error Error during planning: ORDER BY and WITHIN GROUP clauses cannot be used together in the same aggregate function. 
+query error Error during planning: ORDER BY and WITHIN GROUP clauses cannot be used together in the same aggregate function
 SELECT array_agg(a_varchar order by a_varchar) WITHIN GROUP (ORDER BY a_varchar)
 FROM (VALUES ('a'), ('d'), ('c'), ('a')) t(a_varchar);