GitEditor: Convert some one-line slots to lambdas

Change-Id: I83326fbbdd5a43bc29924661b51bae57ecbfe0f9
Reviewed-by: Orgad Shaneh <orgads@gmail.com>

src/plugins/git/giteditor.h

@@ -42,10 +42,6 @@ public:
     void setPlainText(const QString &text) override;
 
 private:
-    void checkoutChange();
-    void cherryPickChange();
-    void revertChange();
-    void logChange();
     void applyDiffChunk(const VcsBase::DiffChunk& chunk, bool revert);
 
     void init() override;