RFR: merge-bot: use correct credentials for listing PRs

[Erik Helin]

Hi all,

please review this small patch that fixes some additional credential confusion
in the merge bot. The bot did not use correct credentials for listing the pull
requests for the target repository.

Thanks,
Erik

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Commits:
 - 509933a7: merge-bot: use correct credentials for listing PRs

Changes: https://git.openjdk.java.net/skara/pull/410/files
 Webrev: https://webrevs.openjdk.java.net/skara/410/webrev.00
  Stats: 8 lines in 1 file changed: 3 ins; 3 del; 2 mod
  Patch: https://git.openjdk.java.net/skara/pull/410.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/410/head:pull/410

PR: https://git.openjdk.java.net/skara/pull/410