fix: notification.vueのIntersectionObserverまわりを修正 (#8010)

* fix notification.vue

* remove a blank line

* disconnect intersection observer

* disconnect2

* Update packages/client/src/components/notification.vue

Co-authored-by: Acid Chicken (硫酸鶏) <root@acid-chicken.com>

* disconnect

* oops

Co-authored-by: Acid Chicken (硫酸鶏) <root@acid-chicken.com>