Update DNS Shotgun parameters for an updated dataset

We've switched to an updated dataset for shotgun jobs. The change in
underlying traffic caused the more sensitive doh-get (and partially dot)
jobs to overload the resolver, making the jobs unstable and unreliable,
due to an increased number of timeouts.

Readjust the load parameters slightly to avoid exceeding ~2 % of
timeouts in the cold cache scenario to stabilize the job results.

(cherry picked from commit 338389b3eb)

.gitlab-ci.yml

@@ -1889,7 +1889,7 @@ shotgun:dot:
   <<: *shotgun_job
   variables:
     SHOTGUN_SCENARIO: dot
-    SHOTGUN_TRAFFIC_MULTIPLIER: 6
+    SHOTGUN_TRAFFIC_MULTIPLIER: 5
   rules: &shotgun_rules_manual_mr
     - if: '$CI_MERGE_REQUEST_DIFF_BASE_SHA != null'
       variables:
@@ -1903,7 +1903,7 @@ shotgun:doh-get:
   <<: *shotgun_job
   variables:
     SHOTGUN_SCENARIO: doh-get
-    SHOTGUN_TRAFFIC_MULTIPLIER: 3
+    SHOTGUN_TRAFFIC_MULTIPLIER: 2
     SHOTGUN_EVAL_THRESHOLD_LATENCY_PCTL_MAX: 0.4  # bump from the default due to increased tail-end jitter
   rules: *shotgun_rules_manual_mr