Don't print stacktrace when it doesn't match the stacktrace regex

What does this MR do and why?

Printing the whole "potential stack trace" can throw stack trace detection that's done when creating incidents, e.g. gitlab-org/quality/engineering-productivity/master-broken-incidents#5198 (comment 1760536845), and doesn't really add any value. We can always check the description of the potential issue, thanks to the => [DEBUG] Stacktrace couldn't be found for <issue url>! debug message.

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