Stale override replaces `discussions` with `team_discussions` in app-permissions

Problem

The override files for /app/installations (scripts/overrides/get-app-installations.json and .deref.json) contain a stale copy of the app-permissions schema that uses team_discussions instead of discussions.

The upstream source (github/rest-api-description) correctly has discussions in its app-permissions schema, but replaceOperation() in scripts/overrides/index.mjs overwrites it with the stale override copy.

Impact

Consumers of @octokit/openapi (e.g. actions/create-github-app-token) that auto-generate permission inputs from app-permissions end up with team_discussions instead of discussions, causing:

• Missing permission-discussions input (users get "Unexpected input" warnings)
• Incorrect permission-team-discussions present instead

Root Cause

The override files were created to fix a anyOf issue (see #305 on openapi-types.ts) but contain a frozen snapshot of the permissions schema from that time. As the upstream schema evolved (team_discussions → discussions), the overrides were never updated.

Fix

Update the two override files to replace team_discussions with discussions (matching the current upstream schema). Also update any other stale permissions that may have drifted.

PR incoming.

Start with scripts/overrides/get-app-installations.json and scripts/overrides/get-app-installations.deref.json, then read replaceOperation() in scripts/overrides/index.mjs and compare the app-permissions schema with the upstream source. Update the stale permission names and check for other permissions that have drifted; done means the overrides match the current upstream schema, including discussions.