Use new static ICore interface.

Change-Id: I9b690d9b150c8d162b15370f9f8986267c9128f1
Reviewed-by: Daniel Teske <daniel.teske@nokia.com>

src/plugins/git/gitclient.h

@@ -293,7 +293,6 @@ private:
     mutable unsigned m_cachedGitVersion;
 
     const QString m_msgWait;
-    Core::ICore *m_core;
     QSignalMapper *m_repositoryChangedSignalMapper;
     GitSettings *m_settings;
 };