[skara] RFR: pr: update error message for backports

[Erik Helin]

Hi all,

please review this patch that fixes the Markdown for the error message when a commit cannot be automatically backported.

Thanks,
Erik

-------------

Commit messages:
 - pr: update error message for backports

Changes: https://git.openjdk.java.net/skara/pull/1101/files
 Webrev: https://webrevs.openjdk.java.net/?repo=skara&pr=1101&range=00
  Stats: 4 lines in 2 files changed: 0 ins; 0 del; 4 mod
  Patch: https://git.openjdk.java.net/skara/pull/1101.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/1101/head:pull/1101

PR: https://git.openjdk.java.net/skara/pull/1101