Currently DevOps does not support limiting service hooks history. The Service Hooks page in the web access admin shows your recent activity (last 14 days) for each subscription, and whether a subscription is enabled, disabled, or restricted.
If you want to limit the number of notifications displayed on the current page, you can use the tab shown in the figure.

If you want to limit the data storage of history for notification (activity), it is recommended that you could submit a feature request on:
https://developercommunity.visualstudio.com/report?space=21&entry=suggestion. Voting helps increase the priority of the issue by consolidating customer impact under one feedback.