RFR: 219: Missing slash before CONTRIBUTING link in /integrate message

[Erik Helin]

Hi all,

please review this small patch that fixes a typo with the URL to the
`COTNRIBUTING.md` file in the new "ready for integration" message.

Thanks,
Erik

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Commits:
 - 990be795: skara-219

Changes: https://git.openjdk.java.net/skara/pull/344/files
 Webrev: https://webrevs.openjdk.java.net/skara/344/webrev.00
  Issue: https://bugs.openjdk.java.net/browse/SKARA-219
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/skara/pull/344.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/344/head:pull/344

PR: https://git.openjdk.java.net/skara/pull/344