flake: TestWorkerConcurrent

Created by: efritz

Example build: https://buildkite.com/sourcegraph/sourcegraph/builds/142037#fae897b1-9931-42ec-864b-34172a3cc879

FAIL | WorkerConcurrent (2.98s)
FAIL |   WorkerConcurrent/numHandlers=4 (0.16s)
FAIL | 	github.com/sourcegraph/sourcegraph/internal/workerutil	3.066s

worker_test.go:219: times 0 (2022-04-13 11:18:28.694910984 +0000 UTC m=+1.084249027-2022-04-13 11:18:28.709918547 +0000 UTC m=+1.099256536) and 8 (2022-04-13 11:18:28.721432647 +0000 UTC m=+1.110770635-2022-04-13 11:18:28.741629988 +0000 UTC m=+1.130967993) failed validation
worker_test.go:219: times 0 (2022-04-13 11:18:28.694910984 +0000 UTC m=+1.084249027-2022-04-13 11:18:28.709918547 +0000 UTC m=+1.099256536) and 9 (2022-04-13 11:18:28.721697667 +0000 UTC m=+1.111035657-2022-04-13 11:18:28.742435832 +0000 UTC m=+1.131773817) failed validation
worker_test.go:219: times 1 (2022-04-13 11:18:28.695350648 +0000 UTC m=+1.084688639-2022-04-13 11:18:28.741464992 +0000 UTC m=+1.130802978) and 9 (2022-04-13 11:18:28.721697667 +0000 UTC m=+1.111035657-2022-04-13 11:18:28.742435832 +0000 UTC m=+1.131773817) failed validation