Various small textual fixes

What has been done in this MR?

• Replace player.name with player.username in the Digsite examination certificates
• Fix some obvious typos in the grand tree quest dialogue (although I would vote to keep "King Nardone" 😁 ), the Entrana monk, slayer gem dialogue
• Replace unicode with ascii in the grand tree quest & plague city quest

What should testers check?

• Confirm that the exam certificates read as, e.g., Player Name, rather than player_name
• No mojibake anywhere in the game (e.g. quotation marks rendering as "’")

• 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.