ci(ctb): Explicitly fail on broken slither detector

The incorrect shift in assembly detector is just broken. Where possible we should otherwise prefer
disabling detectors based on severity (currently only detecting 'high' or via triage mode so that
we can keep detecting other possibly dangerous instances of that detector.

packages/contracts-bedrock/slither.config.json

 {
-  "detectors_to_exclude": "",
+  "detectors_to_exclude": "incorrect-shift-in-assembly",
   "fail_high": true,
   "fail_pedantic": false,
   "exclude_optimization": true,