Remove unused function and change line calc

Using @pijyoi's suggestion regarding line calculation broadcasting

examples/GLLinePlotItem.py

@@ -29,17 +29,14 @@ gz = gl.GLGridItem()
 gz.translate(0, 0, -10)
 w.addItem(gz)
 
-def fn(x, y):
-    return np.cos(np.hypot(x, y))
-
 n = 51
 y = np.linspace(-10,10,n)
 x = np.linspace(-10,10,100)
 for i in range(n):
-    yi = np.array([y[i]]*100)
+    yi = y[i]
     d = np.hypot(x, yi)
     z = 10 * np.cos(d) / (d+1)
-    pts = np.vstack([x,yi,z]).transpose()
+    pts = np.column_stack([x, np.full_like(x, yi), z])
     plt = gl.GLLinePlotItem(pos=pts, color=pg.glColor((i,n*1.3)), width=(i+1)/10., antialias=True)
     w.addItem(plt)