fix: remove the interval specification under spec

Summary

Attempting to install Nexus Repository Manager with the interval key specified directly under spec results in errors when using flux 0.15.0.

Thanks @grant.duncklee for catching this, can you please add the label status::review if the MR is fully complete and ready to be merged.

added statusreview label

added Bug Fixes label

changed milestone to %1.13.0

approved this merge request

merged

mentioned in commit d5a0ae76