Update nats_exporter from 0.12.0 to 0.13.0

[prometheus-rpm-bot]

https://github.com/nats-io/prometheus-nats-exporter/releases/tag/v0.13.0
Release notes:

## Changelog
* 8568b86 Bump golang from 1.20.5-bullseye to 1.21.3-bullseye in /cicd (#259)
* c21cfb2 Bump alpine from 3.18.2 to 3.18.4 in /cicd (#253)
* 31f9a5d Bump docker/setup-buildx-action from 2 to 3 (#252)
* 4de6357 Bump docker/setup-qemu-action from 2 to 3 (#251)
* 83461c2 Bump docker/login-action from 2 to 3 (#250)
* 258c6b4 Bump docker/bake-action from 3 to 4 (#249)
* 2f61087 Bump actions/checkout from 3 to 4 (#248)
* 7bd645a Merge pull request #256 from nats-io/accountsz-metrics
* dcc53f7 fix scraping healthz metrics endpoint (#232)
* 78f05c6 Update dependencies
* 29b22c2 Update licences, minor cleanup
* 923696e Recreate test certs
* 6546411 add /accstatz metrics
* 0fd6d26 Add issue forms (#245)