Update doc/specs/stdlib_constants.md

Co-authored-by: Jeremie Vandenplas <[email protected]>

Author: MilanSkocic

doc/specs/stdlib_constants.md

@@ -9,7 +9,7 @@ title: constants
 
 The [[stdlib_constants]] module provides mathematical constants and the most common physical constants.
 
-The [[stdlib_codata]] module defines all codata constants as derived type [[codata_constant]].
+The [[stdlib_codata]] module defines all codata constants as derived type [[codata_constant_type]].
 The lastest codata constants were released in 2018 by the [NIST](http://physics.nist.gov/constants.)
 The names are quite long and can be aliased with shorter names.