fix: standardize normalize calculation of stddev (#924)

Co-authored-by: Carlos Fuentes <[email protected]>

Author: github-actions[bot]

src/histogram.ts

@@ -77,7 +77,7 @@ export class PiscinaHistogramHandler {
     return {
       average: mean / 1000,
       mean: mean / 1000,
-      stddev,
+      stddev: stddev / 1000,
       min: min / 1000,
       max: max / 1000,
       p0_001: histogram.percentile(0.001) / 1000,