Raise Reassure stability check thresholds to reduce CI flakiness

The stability check compares the same code against itself, so any
deviation is purely CI runner noise. The current 10ms/20% thresholds
are too tight for shared CI runners, causing ~37% false positive
failure rate. Raising to 20ms/40% for the stability check while
keeping 10ms/20% for the actual delta regression check.

Author: abzokhattab

.github/workflows/reassurePerfTests.yml

@@ -35,8 +35,8 @@ jobs:
           retry_on: error
           command: node .github/actions/javascript/reassureStabilityCheck
         env:
-          ALLOWED_DURATION_DEVIATION: 10
-          ALLOWED_RELATIVE_DURATION_DEVIATION: 20
+          ALLOWED_DURATION_DEVIATION: 20
+          ALLOWED_RELATIVE_DURATION_DEVIATION: 40
           IS_VALIDATING_STABILITY: true
 
       - name: Checkout PR head SHA