RFR: git-pr: no need to check forge validity

[Erik Helin]

Hi all,

please review this small patch that removes an superfluous call to
`Forge.isValid` in `git-pr`. `Forge.from` already ensures that the returned
`Forge` is valid, so there is no need for `git-pr` to repeat this check.

Thanks,
Erik

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Commits:
 - 1010210f: git-pr: no need to check forge validity

Changes: https://git.openjdk.java.net/skara/pull/298/files
 Webrev: https://webrevs.openjdk.java.net/skara/298/webrev.00
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/skara/pull/298.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/298/head:pull/298

PR: https://git.openjdk.java.net/skara/pull/298