Update AppSec Custom SAST Rules bot user ID

What does this MR do and why?

The project access token was rotated and a new user ID needs to be set. In its current state the bot can't find its own messages and posts new messages instead of updating the existing ones. (See !122291 (merged))

Resolves gitlab-com/gl-security/appsec/sast-custom-rules#22

Screenshots or screen recordings

N/A

How to set up and validate locally

N/A

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