Change player.name to player.username in Death's message for the holiday random event

What has been done in this MR?

• See title & refer to !1562 (merged) for why I care

What should testers check?

• Do ::hrevent -p player_name -e death and observe that he calls you Player Name rather than Player_name (replace relevant elements in the previous sentence with those from your own username as appropriate). There is no point testing this MR if your tester's player name does not contain spaces/underscores.

• I have tested these changes thoroughly.

• I used the relevant Thanos/Zaros tool for any JSON edits where possible, and have attached screenshots of any changes.