Fix incorrect Google Developers channelId

[TrianguloY]

Description

The snippet in https://developers.google.com/apps-script/advanced/youtube contains this sample code, as a way to subscribe to the Goggle Developers Youtube channel.

When run, the account is subscribed to an unexpected channel:

• Current, wrong: https://www.youtube.com/channel/UC9gFih9rw0zNCK3ZtoKQQyA (JennaMarbles)
• Expected, correct: https://www.youtube.com/channel/UC_x5XG1OV2P6uZZ5FSM9Ttw (Google Developers)

This error exists since at least 5 years ago when 9kopb notified it, but was ignored: 499e650#r45916392

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have performed a peer-reviewed with team member(s)
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• Any dependent changes have been merged and published in downstream modules

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