docs: Add the missing function call to use the signal's actual value

(cherry picked from commit e18aac88d4)

adev/src/content/guide/routing/common-router-tasks.md

@@ -35,7 +35,7 @@ Update the component to have an `input()` property matching the name of the para
 
 ```ts
 id = input.required<string>()
-hero = computed(() => this.service.getHero(id));
+hero = computed(() => this.service.getHero(id()));
 ```
 
 </docs-step>