validation.md: Fix position of skip validation section
validation.md: Fix position of skip validation section

At the moment it appears in the middle of validation section.

Signed-off-by: Edwin Kempin <d43fb6c98c97e553b671ed9a9318100f1de386e7@google.com>
Change-Id: I2ced5de381b7dfbf96d57b915c3be530896eda68

GerritCodeReview/plugins_code-owners,GerritCodeReview/plugins_code-owners,GerritCodeReview/plugins_code-owners,GerritCodeReview/plugins_code-owners