Deskbar: Set no horizontal window size limit in vertical mode

... better so that for scroller arrows will work again.
This regression occurred in hrev53890 trying to fix #15067.

Use B_SIZE_UNLIMITED not -1 for no window size limit.

src/apps/deskbar/BarWindow.cpp

@@ -667,7 +667,7 @@ TBarWindow::SetSizeLimits()
 	} else {
 		if (fBarView->Vertical()) {
 			BWindow::SetSizeLimits(gMinimumWindowWidth, gMaximumWindowWidth,
-				kMenuBarHeight - 1, screenFrame.Height());
+				kMenuBarHeight - 1, B_SIZE_UNLIMITED);
 		} else {
 			BWindow::SetSizeLimits(screenFrame.Width(), screenFrame.Width(),
 				kMenuBarHeight - 1, kMaximumIconSize + 4);