feat: use octokit-from-auth package (#185)

## PR Checklist

- [x] Addresses an existing open issue: fixes #184
- [x] That issue was marked as [`status: accepting
prs`](/~https://github.com/JoshuaKGoldberg/prune-github-notifications/issues?q=is%3Aopen+is%3Aissue+label%3A%22status%3A+accepting+prs%22)
- [x] Steps in
[CONTRIBUTING.md](/~https://github.com/JoshuaKGoldberg/prune-github-notifications/blob/main/.github/CONTRIBUTING.md)
were taken

## Overview

Adds and documents using `octokit-from-auth`.

💖

README.md

@@ -23,18 +23,17 @@
 npx prune-github-notifications
 ```
 
-[`get-github-auth-token`](/~https://github.com/JoshuaKGoldberg/get-github-auth-token) is used to retrieve a GitHub auth token from `process.env.GH_TOKEN` or executing `gh auth token`.
-
 ### CLI Options
 
-| Option        | Type       | Default                                                              | Description                                                   |
-| ------------- | ---------- | -------------------------------------------------------------------- | ------------------------------------------------------------- |
-| `--bandwidth` | `number`   | `6`                                                                  | Maximum parallel requests to start at once.                   |
-| `--reason`    | `string[]` | `["subscribed"]`                                                     | Notification reason(s) to filter to.                          |
-| `--title`     | `string[]` | `["^chore\(deps\): update .+ to", /^build\(deps-dev\): bump .+ to"]` | Notification title regular expressions to filter to.          |
-| `--watch`     | `number`   | `0`                                                                  | A seconds interval to continuously re-run this on, if truthy. |
+| Option        | Type       | Default                                                              | Description                                                                                             |
+| ------------- | ---------- | -------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------- |
+| `--auth`      | `string`   | `process.env.GH_TOKEN` or executing `gh auth token`                  | Auth token for GitHub from [`octokit-from-auth`](/~https://github.com/JoshuaKGoldberg/octokit-from-auth). |
+| `--bandwidth` | `number`   | `6`                                                                  | Maximum parallel requests to start at once.                                                             |
+| `--reason`    | `string[]` | `["subscribed"]`                                                     | Notification reason(s) to filter to.                                                                    |
+| `--title`     | `string[]` | `["^chore\(deps\): update .+ to", /^build\(deps-dev\): bump .+ to"]` | Notification title regular expressions to filter to.                                                    |
+| `--watch`     | `number`   | `0`                                                                  | A seconds interval to continuously re-run this on, if truthy.                                           |
 
-For example, providing all options on the CLI:
+For example, providing all functional options on the CLI:
 
 ```shell
 npx prune-github-notifications --bandwidth 10 --reason subscribed --title "^chore.+ update .+ to"

package.json

@@ -35,8 +35,7 @@
 	},
 	"dependencies": {
 		"chalk": "^5.3.0",
-		"get-github-auth-token": "^0.1.0",
-		"octokit": "^3.1.2",
+		"octokit-from-auth": "^0.2.0",
 		"throttled-queue": "^2.1.4",
 		"zod": "^3.22.4"
 	},