Fix doc typo

Author: jorgebay

doc/features/datatypes/README.md

@@ -12,7 +12,7 @@ counter|[Long / BigInt](numerical)
 date|[LocalDate](datetime)
 decimal|[BigDecimal](numerical)
 double|[Number](numerical)
-duration/[Duration](/api/module.types/class.Duration/)
+duration|[Duration](/api/module.types/class.Duration/)
 float|[Number](numerical)
 inet|[InetAddress](/api/module.types/class.InetAddress/)
 int|[Number](numerical)