clarify effect of explicit arguments

Co-authored-by: Silvan Mosberger <github@infinisil.com>

source/tutorials/callpackage.md

@@ -148,7 +148,7 @@ Hello, people!
 
 This pattern is used widely in Nixpkgs:
 For example, functions which represent Go programs often have a parameter `buildGoModule`.
-It is common to find expressions like `callPackage ./go-program.nix { buildGoModule = buildGo116Module; }` to enforce a certain Go compiler version.
+It is common to find expressions like `callPackage ./go-program.nix { buildGoModule = buildGo116Module; }` to change the default Go compiler version.
 Nixpkgs is therefore not simply a huge library of pre-configured packages, but a collection of functions – package *recipes* – for customising packages and even entire ecosystems (for example "All Python packages using my custom interpreter") on the fly without duplicating code.
 
 # Overrides