RFR: Allow backport from PR

[Jesper Wilhelmsson]

Minor update since the Skara tooling has been updated to allow backports from PRs.

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Commit messages:
 - Allow backport from PR

Changes: https://git.openjdk.org/guide/pull/114/files
 Webrev: https://webrevs.openjdk.org/?repo=guide&pr=114&range=00
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/guide/pull/114.diff
  Fetch: git fetch https://git.openjdk.org/guide.git pull/114/head:pull/114

PR: https://git.openjdk.org/guide/pull/114