Fix leaderboard command issues

[rhaym-tech]

• [x] Removed leaderboard embeds caching: This one has caused many troubles in the leaderboard command generally:
• leaderboard results can be refreshed only after a bot restart while the taken time to retrieve data from DB won't take that long
• the footer returns incorrect command executor infos due to caching the whole embed which contains data of the first command executor since the last bot restart
• [x] Fixed broken reputation leaderboard: Bot were returning fully broken results due to wrong access to User database schema's properties