Leader election cannot be disabled

[kate-osborn]

Describe the bug

NGF does not honor the --leader-election-disable command-line flag.

To Reproduce
Steps to reproduce the behavior:

1. Deploy NGF with leader election disabled.
2. Check NGF logs and see an error related to leader election leases

Expected behavior
If the --leader-election-disable flag is set, NGF should not run in leader election mode.

Your environment

• Version of the NGINX Gateway Fabric - main d76d8eb

Additional context
Likely culprit: https://github.com/nginxinc/nginx-gateway-fabric/blob/d76d8eb455f0ff0ebbce489637aa619376596f87/internal/mode/static/manager.go#L315. Should be set to cfg.LeaderElection.Enable.