review: implement real Spanned for CreateAggregate

Return the name's span instead of Span::empty() to match the
sibling Create* arms.

Author: fmguerreiro

src/ast/spans.rs

@@ -518,7 +518,7 @@ impl Spanned for Statement {
             Statement::Vacuum(..) => Span::empty(),
             Statement::AlterUser(..) => Span::empty(),
             Statement::Reset(..) => Span::empty(),
-            Statement::CreateAggregate(_) => Span::empty(),
+            Statement::CreateAggregate(stmt) => stmt.name.span(),
         }
     }
 }