Show Reject Extension button to staff even when all agreement holders have voted yes

## Bug

On the range use plan list page (`selectRangeUsePlanPage`), when all agreement holders have voted yes on a forward extension request, the **Reject Extension** button is not displayed to staff (SA) users.

### Current behavior

In `src/components/selectRangeUsePlanPage/ExtensionColumn.js`, `renderExtensionForStaff`, when plan `extensionStatus` is `AWAITING_VOTES` and all votes are received (`extensionReceivedVotes >= extensionRequiredVotes`):

- Staff only sees **Forward Extension For Decision**
- The **Reject Extension** button is missing

The Reject Extension button is only shown while votes are incomplete.

### Expected behavior

Staff should be able to reject the extension even when all agreement holders have voted yes, so **Reject Extension** must be displayed alongside **Forward Extension For Decision** in that state.

### Notes

- Regression introduced by #1182 (hide reject button from staff once all RAH approved) + #1293 (`===` -> `>=`).
- Also present in the `dev` branch equivalent (`ExtensionColumn.tsx`).

Start in src/components/selectRangeUsePlanPage/ExtensionColumn.js and inspect renderExtensionForStaff for the AWAITING_VOTES state when extensionReceivedVotes >= extensionRequiredVotes. Compare the equivalent ExtensionColumn.tsx in the dev branch if useful. Done means staff see both Reject Extension and Forward Extension For Decision when all agreement holders have voted yes.

Written by the indexing model from the issue text.