Increase NGINX ingress error log level from notice to error

What does this MR do?

The default value of notice may be hiding some important errors. We did this in production with gitlab-com/gl-infra/k8s-workloads/gitlab-com!4779 (merged).

References:

• https://github.com/kubernetes/ingress-nginx/blob/main/docs/user-guide/nginx-configuration/configmap.md#configmaps
• https://nginx.org/en/docs/ngx_core_module.html#error_log

Related issues

Author checklist

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Required

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• Merge Request Title and Description are up to date, accurate, and descriptive.
• MR targeting the appropriate branch.
• MR has a green pipeline.
• Documentation created/updated.
• Tests added/updated, and test plan for scenarios not covered by automated tests.
• Equivalent MR/issue for omnibus-gitlab opened.

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• MR has a green pipeline on https://gitlab.com/gitlab-org/charts/gitlab.
• Consider downstream impact to the Operator, as per evaluating impact from changes to GitLab chart.