module system intro: simplify to just type constraint

it doesn't matter here that the type constraint is dynamic,
and the extra qualifier is probably mostly confusing for beginners,
also, everything in the language is dynamic anyway.

Author: fricklerhandwerk

source/tutorials/module-system/index.md

@@ -5,7 +5,7 @@ Much of the power in Nixpkgs and NixOS comes from the module system.
 
 The module system is a Nix language library that enables you to
 - Declare one attribute set using many separate Nix expressions.
-- Impose dynamic type constraints on values in that attribute set.
+- Impose type constraints on values in that attribute set.
 - Define values for the same attribute in different Nix expressions and merge these values automatically according to their type.
 
 These Nix expressions are called modules and must have a particular structure.