Fix migration logic for old player saving config option

This is an ode to all those times when you shoulda just gone to bed

patches/server/Upstream-config-migrations.patch

@@ -19,8 +19,9 @@ index 0000000000000000000000000000000000000000..00000000000000000000000000000000
 +        Object val = config.get("settings.save-player-data");
 +        if (val instanceof Boolean) {
 +            SpigotConfig.disablePlayerDataSaving = !(Boolean) val;
-+            SpigotConfig.config.set("players.disable-saving", SpigotConfig.disableAdvancementSaving);
++            SpigotConfig.config.set("players.disable-saving", SpigotConfig.disablePlayerDataSaving);
 +            SpigotConfig.save();
++            config.set("settings.save-player-data", null);
 +        }
 +    }
 +