Raise arch-pkg-repo-updater service's ulimit

The arch-pkg-repo-updater service used by bumpbuddy to pull changes on local repo clones is facing some "Too many open files" issues on a semi-regular basis:

Aug 28 18:28:14 bumpbuddy.archlinux.org systemd[1]: Starting arch-pkg-repo-updater.service...
Aug 28 18:28:14 bumpbuddy.archlinux.org ssh-agent[1738851]: Identity added: /home/bumpbuddy/.ssh/id_ed25519 (bumpbuddy@bumpbuddy.archlinux.org)
Aug 28 18:28:14 bumpbuddy.archlinux.org ssh-agent[1738836]: 2025-08-28T18:28:14.382920Z  INFO buildbtw_poc::gitlab: Querying changed projects since Some(2025-08-28 18:14:22.0 +00:00:00)
Aug 28 18:28:14 bumpbuddy.archlinux.org ssh-agent[1738836]: 2025-08-28T18:28:14.382994Z  INFO gitlab: sending GraphQL query 'ChangedProjects' Variables { after: None, group: "archlinux/pac>
Aug 28 18:28:15 bumpbuddy.archlinux.org ssh-agent[1738836]: 2025-08-28T18:28:15.082015Z  INFO buildbtw_poc::gitlab: 47 changed source repos found (first: Some(ChangedProjectsGroupProjectsN>
Aug 28 18:28:15 bumpbuddy.archlinux.org ssh-agent[1738836]: The application panicked (crashed).
Aug 28 18:28:16 bumpbuddy.archlinux.org ssh-agent[1738836]: Message:  Failed to fetch repository:
Aug 28 18:28:16 bumpbuddy.archlinux.org ssh-agent[1738836]:    0: could not open '/opt/bumpbuddy/source_repos/glirc/.git/refs/tags/2.39.0.1-224': Too many open files; class=Os (2)
Aug 28 18:28:16 bumpbuddy.archlinux.org ssh-agent[1738836]: Location:
Aug 28 18:28:16 bumpbuddy.archlinux.org ssh-agent[1738836]:    /usr/src/debug/arch-pkg-repo-updater/buildbtw/buildbtw-poc/src/git.rs:81
Aug 28 18:28:16 bumpbuddy.archlinux.org ssh-agent[1738836]: Backtrace omitted. Run with RUST_BACKTRACE=1 environment variable to display it.
Aug 28 18:28:16 bumpbuddy.archlinux.org ssh-agent[1738836]: Run with RUST_BACKTRACE=full to include source snippets.
Aug 28 18:28:16 bumpbuddy.archlinux.org ssh-agent[1738836]: Location: /usr/src/debug/arch-pkg-repo-updater/buildbtw/buildbtw-poc/src/git.rs:101
Aug 28 18:28:16 bumpbuddy.archlinux.org ssh-agent[1738836]: Backtrace omitted. Run with RUST_BACKTRACE=1 environment variable to display it.
Aug 28 18:28:16 bumpbuddy.archlinux.org ssh-agent[1738836]: Run with RUST_BACKTRACE=full to include source snippets.
Aug 28 18:28:19 bumpbuddy.archlinux.org ssh-agent[1738836]: Error:
Aug 28 18:28:19 bumpbuddy.archlinux.org ssh-agent[1738836]:    0: task 38 panicked with message "Failed to fetch repository: \n   0: \u{1b}[91mcould not open '/opt/bumpbuddy/source_repos/h>
Aug 28 18:28:19 bumpbuddy.archlinux.org ssh-agent[1738836]: Location:
Aug 28 18:28:19 bumpbuddy.archlinux.org ssh-agent[1738836]:    /usr/src/debug/arch-pkg-repo-updater/buildbtw/buildbtw-poc/src/git.rs:58
Aug 28 18:28:19 bumpbuddy.archlinux.org ssh-agent[1738836]: Backtrace omitted. Run with RUST_BACKTRACE=1 environment variable to display it.
Aug 28 18:28:19 bumpbuddy.archlinux.org ssh-agent[1738836]: Run with RUST_BACKTRACE=full to include source snippets.
Aug 28 18:28:19 bumpbuddy.archlinux.org systemd[1]: arch-pkg-repo-updater.service: Main process exited, code=exited, status=1/FAILURE
Aug 28 18:28:19 bumpbuddy.archlinux.org systemd[1]: arch-pkg-repo-updater.service: Failed with result 'exit-code'.
Aug 28 18:28:19 bumpbuddy.archlinux.org systemd[1]: Failed to start arch-pkg-repo-updater.service.
Aug 28 18:28:19 bumpbuddy.archlinux.org systemd[1]: arch-pkg-repo-updater.service: Consumed 5.373s CPU time, 165M memory peak.

Raising the ulimit should hopefully help.