go.dev: decrease HaTS sample size

We're getting more responses than we need for go.dev HaTS.
Decreasing the sample size from 40% to 10%.

Change-Id: I9aae64db6a675da27823ad6f4b006f6dd44ce1bf
Reviewed-on: https://go-review.googlesource.com/c/website/+/362954
Trust: Jamal Carvalho <jamal@golang.org>
Run-TryBot: Jamal Carvalho <jamal@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>

go.dev/_content/js/hats.js

@@ -55,7 +55,7 @@ function requestHaTs(cookieName, triggerId, bucketSample, promptSample) {
 
 (function () {
   // HaTS - go.dev
-  requestHaTs('HaTS_BKT', 'RLVVv5Lf10njVvnD1rP0QUpmtosS', 0.4, 0.5);
+  requestHaTs('HaTS_BKT', 'RLVVv5Lf10njVvnD1rP0QUpmtosS', 0.1, 0.5);
 
   // All download links on the go.dev homepage may trigger a survey.
   [