Address security-managers API deprecation

## Problem Description
Safe-settings logs are showing a deprecation message from Github about the `security-managers` endpoint being removed on Jan 1, 2026.

I see in the code that there is a [commented-out fix to address this](https://github.com/github/safe-settings/blob/594f3c706de6c4ddafb1a86dfa7468f19337e54f/lib/plugins/teams.js#L17), but I didn't find an open issue or PR with a planned change.

### What is actually happening
Warning in logs

### What is the expected behavior
No warning and safe-settings continues to work after Jan 1, 2026

### Error output, if available
```
[@octokit/request] "GET https://api.github.com/orgs/imprivata-ai/security-managers" is deprecated. It is scheduled to be removed on Thu, 01 Jan 2026 00:00:00 GMT. See https://gh.io/security-managers-rest-api-sunset
```

## Context

### Are you using the hosted instance of probot/settings or running your own?
self-run via GHA

### If running your own instance, are you using it with github.com or GitHub Enterprise?
github.com

#### Version of probot/settings
n/a

#### Version of GitHub Enterprise
n/a