Investigate knapsack test splitting taking longer for smoke

From gitlab-org/quality&184 (comment 2642659706), it was found that smoke tests are taking longer to run than in the past. This ticket is to investigate and ideally unravel why this is from a knapsack test splitting perspective. Here, test splitting with knapsack is taking ~5m30s more:

old: https://pipeline-visualizer-gitlab-org-quality-engineeri-bcf92e4999c4df.gitlab.io/gitlab-org/quality/staging-canary/pipeline/4333834

current: https://pipeline-visualizer-gitlab-org-quality-engineeri-bcf92e4999c4df.gitlab.io/gitlab-org/quality/staging-canary/pipeline/4755428