Errors in BT-17-Lot, BT-25, BT-26(a), BT-26(m)

[duncandewhurst]

Noting for posterity that I corrected a few errors I spotted whilst working on updates to the lots extension:

44b2900:

• BT-17-Lot: Remove reference to deprecated tender.submissionMethod.

9f21ea9:

• BT-25: Remove reference to Item.relatedLots
• BT-25, 26(a), 26(m): Replace Item.relatedLots with Item.relatedLot in examples