RFR: 1636: Revert GitLab workaround when modifying labels

[Erik Joelsson]

The workaround for GitLab returning 500 when modifying labels is not longer needed ([SKARA-1612](https://bugs.openjdk.org/browse/SKARA-1612)).

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Commit messages:
 - SKARA-1636

Changes: https://git.openjdk.org/skara/pull/1398/files
 Webrev: https://webrevs.openjdk.org/?repo=skara&pr=1398&range=00
  Issue: https://bugs.openjdk.org/browse/SKARA-1636
  Stats: 16 lines in 1 file changed: 0 ins; 16 del; 0 mod
  Patch: https://git.openjdk.org/skara/pull/1398.diff
  Fetch: git fetch https://git.openjdk.org/skara pull/1398/head:pull/1398

PR: https://git.openjdk.org/skara/pull/1398