Clean headers in Git.

Ran script to remove inludes on a trial-and-error basis and
manually corrected it.

Change-Id: Ib2afbc530760684db96888b927c5153b29fe24aa
Reviewed-by: Tobias Hunger <tobias.hunger@digia.com>

src/plugins/git/branchdialog.cpp

@@ -37,12 +37,10 @@
 #include "ui_branchdialog.h"
 #include "stashdialog.h" // Label helpers
 
-#include <utils/checkablemessagebox.h>
 #include <utils/qtcassert.h>
 #include <vcsbase/vcsbaseoutputwindow.h>
 
 #include <QItemSelectionModel>
-#include <QPushButton>
 #include <QMessageBox>
 #include <QList>