RFR: pr: markdown fixes for /backport

[Erik Helin]

Hi all,

please review this patch that contains minor markdown fixes for the `/backport` command.

Thanks,
Erik

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Commit messages:
 - pr: markdown fixes for /backport

Changes: https://git.openjdk.java.net/skara/pull/1126/files
 Webrev: https://webrevs.openjdk.java.net/?repo=skara&pr=1126&range=00
  Stats: 8 lines in 1 file changed: 1 ins; 4 del; 3 mod
  Patch: https://git.openjdk.java.net/skara/pull/1126.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/1126/head:pull/1126

PR: https://git.openjdk.java.net/skara/pull/1126