let people go negative to fix certain exploits

This allows people to go negative to fix 1 of the 2 main methods for duplicating money in DarkRP

by default, darkrp doesn't seem to set the "wallet" column to unsigned anywhere so no need to alter tables
I also confirmed I was able to do the following w/o having my money reset:
- leave & immediately rejoin
- restart the server w/o leaving (via _restart specifically)
- leave then restart the server

gamemode/modules/base/sv_data.lua

@@ -389,7 +389,7 @@ function DarkRP.createPlayerData(ply, name, wallet, salary)
 end
 
 function DarkRP.storeMoney(ply, amount)
-    if not isnumber(amount) or amount < 0 or amount >= 1 / 0 then return end
+    if not isnumber(amount) or amount >= 1 / 0 then return end
 
     -- Also keep deprecated UniqueID data at least somewhat up to date
     MySQLite.query([[UPDATE darkrp_player SET wallet = ]] .. amount .. [[ WHERE uid = ]] .. ply:UniqueID() .. [[ OR uid = ]] .. ply:SteamID64())