mesa: don't save/restore VAO NumUpdates and IsDynamic to fix update tracking

NumUpdates is used to indicate whether a VAO is static or dynamic, but if
we restored an older value, it could incorrectly indicate that it's not
dynamic.

This fixes a small performance issue with torcs.

Acked-by: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/10994>

src/mesa/main/attrib.c

@@ -1359,8 +1359,7 @@ copy_array_object(struct gl_context *ctx,
    dest->NonZeroDivisorMask = src->NonZeroDivisorMask;
    dest->_AttributeMapMode = src->_AttributeMapMode;
    dest->NewArrays = src->NewArrays;
-   dest->NumUpdates = src->NumUpdates;
-   dest->IsDynamic = src->IsDynamic;
+   /* skip NumUpdates and IsDynamic because they can only increase, not decrease */
 }
 
 /**