mesa: remove call to Driver.Scissor() in _mesa_WindowRectanglesEXT()

This is actually useless because this driver call is only used
by the classic DRI drivers which don't support that extension
and probably won't never support it.

Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>

src/mesa/main/scissor.c

@@ -258,9 +258,6 @@ _mesa_WindowRectanglesEXT(GLenum mode, GLsizei count, const GLint *box)
           sizeof(struct gl_scissor_rect) * count);
    ctx->Scissor.NumWindowRects = count;
    ctx->Scissor.WindowRectMode = mode;
-
-   if (ctx->Driver.Scissor)
-      ctx->Driver.Scissor(ctx);
 }