mesa: remove MAX_VERTEX_PROGRAM_ATTRIBS

Use MAX_VERTEX_GENERIC_ATTRIBS instead.  No need for two #defines for
the same quantity.
diff --git a/src/mesa/shader/arbprogram.c b/src/mesa/shader/arbprogram.c
index 6f5a954..21c5cfb 100644
--- a/src/mesa/shader/arbprogram.c
+++ b/src/mesa/shader/arbprogram.c
@@ -310,7 +310,7 @@
    GET_CURRENT_CONTEXT(ctx);
    ASSERT_OUTSIDE_BEGIN_END(ctx);
 
-   if (index >= MAX_VERTEX_PROGRAM_ATTRIBS) {
+   if (index >= MAX_VERTEX_GENERIC_ATTRIBS) {
       _mesa_error(ctx, GL_INVALID_VALUE, "glGetVertexAttribfvARB(index)");
       return;
    }