Fix typo in Stages

Author: Psychpsyo

Stages.md

@@ -21,7 +21,7 @@ These checkpoints are modeled loosely on the [TC39 process](https://tc39.es/proc
 * It is expected that the [Contributor](./IPR%20Policy.md#contributor) will champion the [Contribution](./IPR%20Policy.md#21-contribution), through answering questions asynchronously, providing feedback when requested, and consideration of important open questions at triage meetings.
 * Anyone can review and submit feedback on [Contributions](./IPR%20Policy.md#21-contribution).
 * Stage level is tracked with labels on issues on the relevant standard — “stage 0”, “stage 1”, etc.
-* Stage labels (other than stage 0) should only be added by browser engine representatives, or by Editors of the relevant standard, necessary support for a level has been demonstrated.
+* Stage labels (other than stage 0) should only be added by browser engine representatives, or by Editors of the relevant standard, once necessary support for a level has been demonstrated.
 * This process is subject to and governed by [WHATWG Policies](./Policies.md), including the [Intellectual Property Rights Policy](./IPR%20Policy.md).
 * **Advancing stages**
     * The [Contributor](./IPR%20Policy.md#contributor) should bring the [Contribution](./IPR%20Policy.md#21-contribution) to the WHATWG to advance to the next stage by setting an “Agenda+” label on the tracking issue, and showing up to (or ensuring someone will show up to) the next triage meeting to discuss. Advancing to a new stage requires support for the decision by at least two implementers (via their browser engine representatives), and there should not be any strong implementer objections ([per the working mode](./Working%20Mode.md#additions). This support can also be gathered in any public manner, e.g., GitHub issue comments, triage meetings, etc.