Remove unused Twenty Partner Ops role from twenty-partners app (1.6.5) (#24764)

## What

Releases `twenty-partners` 1.6.5, which removes the `Twenty Partner Ops`
role from the app:

- Delete `src/roles/twenty-partner-ops.role.ts` and its
`TWENTY_PARTNER_OPS_ROLE_UNIVERSAL_IDENTIFIER` constant.
- Update the workflows README table ("Admin / Partner Ops" -> "Admin").
- Set `canBeAssignedToUsers: false` on the app's default function role
so it can't be hand-assigned to users.
- Bump the app version to 1.6.5.

## Why

The role has zero workspace members, zero agents, and zero API keys
assigned in the production partners workspace — the Twenty team operates
on the built-in Admin role instead. Removing it from the manifest lets
the next app publish delete the role server-side via application sync.
Safe because the sync deletion path cascade-removes role targets, and
there are none.

The application default role ("Twenty partners default function role")
is intentionally kept: the app's serverless functions execute under it
and the SDK build requires exactly one `defineApplicationRole`. The
`Partner` role is untouched.

The leftover workspace-bootstrap `Member` role was already deleted
directly in the prod workspace (not app-managed, so no code change).

## Verification

- 230/230 unit tests pass in the app package.
- `tsc --noEmit` clean.
- `twenty dev:build` manifest build succeeds and contains exactly two
roles: `Partner` and the default function role.