test: decrease runtime metrics flakiness on windows (#6998)

The generic overhead on Windows is higher than unix based platforms.

Author: BridgeAR

packages/dd-trace/test/runtime_metrics.spec.js

@@ -526,7 +526,8 @@ function createGarbage (count = 50) {
                 )
                 totalPercent = number
               }
-              assert(number - expected < 0.5, `${metric} sanity check failed: ${number} ${expected}`)
+              const epsilon = os.platform() === 'win32' ? 1.5 : 0.5
+              assert(number - expected < epsilon, `${metric} sanity check failed: ${number} ${expected}`)
             }
           }