Fix misunderstanding about for..of with plain objects in iterables article

[krakowdeveloper]

Description:
This PR corrects a fundamental misunderstanding in the article about how for..of works with plain objects. The current explanation could lead readers to believe that:

Plain objects work with for..of by default (they don't - they must implement Symbol.iterator)

The iteration protocol is unclear before introducing Symbol.iterator

• Improvements:

Clarifies that plain objects are NOT iterable by default
Better explains the relationship between objects, iterables, and iterators
Provides accurate examples showing the TypeError that occurs without proper implementation
Maintains all existing correct information while fixing the misconceptions

Before diving into implementation details, we now properly establish what doesn't work and why.

[CLAassistant]

All committers have signed the CLA.

[krakowdeveloper]

how long takes a review?

[iliakan]

I like the previous version more. It's differently phrased.

Maybe I'm biased toward my own text? :/
Open to suggestions.

[joaquinelio]

IMHO
I like the flow of the original
and I dont see it suggests it's iterable by default

but there may be a point
I would accept the change in line 8, it dissipates any doubt

[krakowdeveloper]

I like the previous version more. It's differently phrased.

Maybe I'm biased toward my own text? :/ Open to suggestions.

for..of doesn't works in objects. And the purpose of "iterables" title in your documentation, is more about how to convert" an object to be itereable and make use of the for ...of. which deserve also another title and point to one of the Symbols well known features. Of course is your repo, but it is wrong information. for of only produce typeError:
const obj = {a: 1, b: 2};
for (const item of obj) { // TypeError: obj is not iterable
console.log(item);
}

your article suggest suitable use for..of over objects at the whole intro article. This is not connected to you, is how javascript works.

[krakowdeveloper]

IMHO I like the flow of the original and I dont see it suggests it's iterable by default

but there may be a point I would accept the change in line 8, it dissipates any doubt

the version I get online says: Iterable objects are a generalization of arrays. That’s a concept that allows us to make any object useable in a for..of loop.

2. If an object isn’t technically an array, but represents a collection (list, set) of something, then for..of is a great syntax to loop over it, so let’s see how to make it work.

• a collection of something is also an object and for..of produce TypeError, which is: NOT great syntax to loop over it :)