remove superfluous language in Using Web Workers (mdn#8997)

In the sentence `To illustrate this, let's create for didactical purpose a function named emulateMessage()`, "for didactical purpose" is an unusual and confusing phrase. luckily it's also unnecessary, since the beginning of the sentence "To illustrate this" conveys the same meaning already, ie "for example"

files/en-us/web/api/web_workers_api/using_web_workers/index.md

@@ -235,7 +235,7 @@ The exception to this is if the worker script's origin is a globally unique iden
 
 Data passed between the main page and workers is **copied**, not shared. Objects are serialized as they're handed to the worker, and subsequently, de-serialized on the other end. The page and worker **do not share the same instance**, so the end result is that **a duplicate** is created on each end. Most browsers implement this feature as [structured cloning](/en-US/docs/Web/API/Web_Workers_API/Structured_clone_algorithm).
 
-To illustrate this, let's create for didactical purpose a function named `emulateMessage()`, which will simulate the behavior of a value that is _cloned and not shared_ during the passage from a `worker` to the main page or vice versa:
+To illustrate this, let's create a function named `emulateMessage()`, which will simulate the behavior of a value that is _cloned and not shared_ during the passage from a `worker` to the main page or vice versa:
 
 ```js
 function emulateMessage(vVal) {