Terminal: set B_NO_BORDER on the tab view.

This looks better and is what we want here. The difference is subtle,
just a few pixels on the left and right side of the tabview where it now
properly joins the window border.

src/apps/terminal/SmartTabView.cpp

@@ -165,6 +165,8 @@ SmartTabView::AddTab(BView* target, BTab* tab)
 				bar->MoveBy(0, 1);
 			}
 		}
+
+		SetBorder(B_NO_BORDER);
 	}
 
 	Invalidate(TabFrame(CountTabs() - 1).InsetByCopy(-2, -2));