Sign-up form: Remove password match validation message from image

[MaoShizhong]

Because

#28056 removed the "matching passwords" validation instruction from the sign-up form project because it requires JS and gets taught later in the JS course. The image was overlooked so not updated to reflect that removal. I've seen a couple of learners caught out by this and still trying to implement matching password validation because the image implies its necessity.

This PR

• Removes the matching password validation error message from the design image.

Issue

N/A

Additional Information

Will open a 2nd PR with the statically link change once merged.

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