Working with APIs: Clarify default 'cors' mode behavior in CORS section

[Maddily]

Because

I wanted to mention the default behavior when sending cross-origin requests using fetch.

This PR

• Mentions that, in case the request being sent is cross-origin, mode: 'cors'` is set by default.
• Adds that explicitly specifying mode: 'cors' in the options is good for clarity.

Issue

Closes #XXXXX

Additional Information

N/A

Pull Request Requirements

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[MaoShizhong]

We can actually probably just remove the { mode: 'cors' } bits entirely (from this lesson and a few other lessons in the curriculum) as that's the default mode for fetch. So the CORS section introducing that to "solve a problem" is redundant because there is no problem when omitted.

If you can put this on hold for a bit, I'm discussing with the team regarding some other CORS material because there might be an additional thing we need to do on top of removing the mode options references. I'll get back to you once we've discussed that through.

[Maddily]

That makes sense. I'll put this on hold for now and wait for your update after the team discussion.

[Mclilzee]

@MaoShizhong There was an Issue + PR I opened regarding this in the past. Maybe it is worth looking into why it was closed and not merged Check #23232