mesa: remove spurious flush in _mesa_DepthRange()

I don't think this is actually required, if the depth range
values are different from the ones stored in the context, we
already flush and trigger _NEW_VIEWPORT in
set_depth_range_no_notify().

Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Brian Paul <brianp@vmware.com>

src/mesa/main/viewport.c

@@ -319,8 +319,6 @@ _mesa_DepthRange(GLclampd nearval, GLclampd farval)
    unsigned i;
    GET_CURRENT_CONTEXT(ctx);
 
-   FLUSH_VERTICES(ctx, 0);
-
    if (MESA_VERBOSE&VERBOSE_API)
       _mesa_debug(ctx, "glDepthRange %f %f\n", nearval, farval);