pci: remove Link Training error from AER error list

The spec says:

    Undefined – The value read from this bit is
    undefined. In previous versions of this
    specification, this bit was used to indicate a Link
    Training Error. System software must ignore the
    value read from this bit. System software is
    permitted to write any value to this bit.

Do not allow injecting it.
Suggested-by: NMichael S. Tsirkin <mst@redhat.com>
Reviewed-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

hw/pci/pcie_aer.c

@@ -827,10 +827,6 @@ typedef struct PCIEAERErrorName {
  */
 static const struct PCIEAERErrorName pcie_aer_error_list[] = {
     {
-        .name = "TRAIN",
-        .val = PCI_ERR_UNC_TRAIN,
-        .correctable = false,
-    }, {
         .name = "DLP",
         .val = PCI_ERR_UNC_DLP,
         .correctable = false,