RFR: Ensure that labels do not propagate to backports [v2]

[Robin Westberg]

> If the backport creation endpoint does not clear the labels, we can do it manually.

Robin Westberg has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase.

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Changes:
  - all: https://git.openjdk.java.net/skara/pull/965/files
  - new: https://git.openjdk.java.net/skara/pull/965/files/3dde36a2..3dde36a2

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=skara&pr=965&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=skara&pr=965&range=00-01

  Stats: 0 lines in 0 files changed: 0 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/skara/pull/965.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/965/head:pull/965

PR: https://git.openjdk.java.net/skara/pull/965