Update instructions to reset password on GDK

What does this MR do and why?

While trying to update the password on my local GDK, I found the instructions to be confusing being a non-technical contributor. @jivanvl helped me with a different command that helped me change the password with added convenience and ease. Appending the same to the guidelines.

Describe in detail what your merge request does and why.

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How to set up and validate locally

There's no local validation needed as this is a docs improvement Numbered steps to set up and validate the change are strongly suggested.

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