ci: remove useless whitespace in the .gitlab-ci.yml

1 job for 38-allow-any-date-column-name-for-the-obsdf-argument-of-the-shinygr-function in 1 minute and 41 seconds (queued for 3 seconds)
Status Name Job ID Coverage
  Check
passed check_as_cran_patched #176996

00:01:41