Hello dense_data,
Starting from PhotoScan version 1.4.2 (both Standard and Professional) you can modify that "hidden"setting using Tweaks dialog that is accessible from the Advanced Preferences tab.
Create the new entry with the following name:
main/dense_cloud_max_neighbors
and assign the desired pairs value, like 50 or 60, for example.
To remove the limit you can either delete the "tweak" or set the value to "-1".