If you have nothing to do with the time-sensitive Snapchat feature then it is better to turn this feature off to get rid of the unwanted Snapchat notifications. These are the steps:
Open the settings of your iPhone.
Search for the Snapchat application.
Tap the notification option in the Snapchat settings.
Finally, you have the option where you can disable the time-sensitive notifications.
Read more if you want to know more:
https://ityug247.com/what-does-time-sensitive-mean-on-snapchat