fix(workflow): Remove noisy DetectorGroup.DoesNotExist log

[sentry]

The `_get_detector_for_group` function in `sentry/workflow_engine/processors/detector.py` was logging `DetectorGroup.DoesNotExist` as an exception. This `DoesNotExist` is an expected fallback path when a group does not have a specific `DetectorGroup` associated with it, and the system correctly falls back to project-level or issue stream detectors.

Logging this as an exception was generating a large volume of non-actionable error events in Sentry. This change removes the log statement entirely, as the absence of a DetectorGroup is a normal and handled condition, not an error.

Legal Boilerplate

Look, I get it. The entity doing business as "Sentry" was incorporated in the State of Delaware in 2015 as Functional Software, Inc. and is gonna need some rights from me in order to utilize my contributions in this here PR. So here's the deal: I retain all rights, title and interest in and to my contributions, and by keeping this boilerplate intact I confirm that Sentry can use, modify, copy, and redistribute my contributions, under Sentry's choice of terms.

Fixes SENTRY-5R4N

_{Comment @sentry <feedback> on this PR to have Autofix iterate on the changes.}

[saponifi3d]

lgtm - but i'd also be okay with us just removing this log tbh.