fix the memleak

src/main.zig

@@ -99,6 +99,7 @@ pub fn main() !void {
                 if (ret == c.FALSE) {
                     std.log.err("failed to send a notification: {s}", .{g_err.*.message});
                 }
+                c.g_object_unref(c.G_OBJECT(notif));
 
                 std.log.info("[NOTIFY] battery running low!", .{});
             }