RFR: forge: fix GitHubRepository.createPullRequestUrl

[Erik Helin]

Hi all,

please review this patch that fixes `GitHubRepository.createPullRequestUrl` (I had forgotten a `/pull/`) in the URL. Thanks to @RealCLanger for finding this!

Erik

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Commit messages:
 - forge: fix GitHubRepository.createPullRequestUrl

Changes: https://git.openjdk.java.net/skara/pull/1145/files
 Webrev: https://webrevs.openjdk.java.net/?repo=skara&pr=1145&range=00
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/skara/pull/1145.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/1145/head:pull/1145

PR: https://git.openjdk.java.net/skara/pull/1145