git-gui: use full dialog width for old name when renaming branch

Let the combobox/option menu expand to fill the width of the dialog.
Signed-off-by: NPat Thoyts <patthoyts@users.sourceforge.net>

lib/branch_rename.tcl

@@ -53,7 +53,7 @@ constructor dialog {} {
 			return 1
 		}
 
-	grid $w.rename.oldname_l $w.rename.oldname_m -sticky w  -padx {0 5}
+	grid $w.rename.oldname_l $w.rename.oldname_m -sticky we -padx {0 5}
 	grid $w.rename.newname_l $w.rename.newname_t -sticky we -padx {0 5}
 	grid columnconfigure $w.rename 1 -weight 1
 	pack $w.rename -anchor nw -fill x -pady 5 -padx 5