Raise timeout in Workhorse object storage test

What does this MR do and why?

Previously this test was failing intermittently in the race detector job since the 0.001 s timeout not give much time for the HTTP server to establish a connection. Raise the timeout to 0.1 s to improve the reliability of the test.

Relates to #378802 (closed)

How to set up and validate locally

Run the script:

set -e

while true
do
  go test -count 1 -v -race -timeout 30s -run ^TestUploadHandlerSendingToExternalStorageAndSupportRequestTimeout$ gitlab.com/gitlab-org/gitlab/workhorse/internal/upload
done

MR acceptance checklist

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