doc(pipes): copyedit and remove Jade block used for Data (#3306)

- JS event --> DOM event
- The Jade block isn't used by Dart anymore.
- In `learning-angular.jade`, removed trailing whitespace.

public/docs/ts/latest/guide/pipes.jade

@@ -197,7 +197,7 @@ a#change-detection
 :marked
   ## Pipes and change detection
 
-  Angular looks for changes to data-bound values through a *change detection* process that runs after every JavaScript event:
+  Angular looks for changes to data-bound values through a *change detection* process that runs after every DOM event:
   every keystroke, mouse move, timer tick, and server response. This could be expensive.
   Angular strives to lower the cost whenever possible and appropriate.
 
@@ -284,13 +284,10 @@ figure.image-display
 
   ### Pure pipes
 
-block pure-change
-  :marked
   Angular executes a *pure pipe* only when it detects a *pure change* to the input value.
   A pure change is either a change to a primitive input value (`String`, `Number`, `Boolean`, `Symbol`)
   or a changed object reference (`Date`, `Array`, `Function`, `Object`).
 
-:marked
   Angular ignores changes within (composite) objects.
   It won't call a pure pipe if you change an input month, add to an input #{_array}, or update an input object property.