Allow grep-ing for on_grant and on_revoke (#8958)

Just two code comments are added.

builtin/game/chat.lua

@@ -186,6 +186,7 @@ local function handle_grant_command(caller, grantname, grantprivstr)
 		return false, privs_unknown
 	end
 	for priv, _ in pairs(grantprivs) do
+		-- call the on_grant callbacks
 		core.run_priv_callbacks(grantname, priv, caller, "grant")
 	end
 	core.set_player_privs(grantname, privs)
@@ -258,6 +259,7 @@ core.register_chatcommand("revoke", {
 		end
 
 		for priv, _ in pairs(revoke_privs) do
+			-- call the on_revoke callbacks
 			core.run_priv_callbacks(revoke_name, priv, name, "revoke")
 		end