Remove unreachable values in mobility table

The possible maximum mobility cardinality (plus one in case of
zero squares available) is:

- Knights: max. 8  squares -> max. 9  entries
- Bishops: max. 13 squares -> max. 14 entries
- Rooks:   max. 14 squares -> max. 15 entries
- Queen:   max. 27 squares -> max. 28 entries

So remove the extra entries in the table.

Spotted by Dariusz Orzechowski.

No functional change.