gitk: Use the -q flag to git checkout

This avoids having gitk think that an error has occurred in the checkout.

Signed-off-by: Paul Mackerras <[email protected]>

Author: paulusmack

gitk

@@ -5356,7 +5356,7 @@ proc cobranch {} {
     nowbusy checkout
     update
     if {[catch {
-	exec git checkout $headmenuhead
+	exec git checkout -q $headmenuhead
     } err]} {
 	notbusy checkout
 	error_popup $err