MetaMetrics event fragment timeout check mixes milliseconds and seconds

I think the event fragment timeout check in MetaMetrics is using the wrong unit conversion.

Current code in `app/scripts/controllers/metametrics-controller.ts`:

```ts
Date.now() - fragment.lastUpdated / 1000 > fragment.timeout
```

But the fragment contract says:

- `timeout` is in seconds
- `lastUpdated` is `Date.now()`

From `shared/constants/metametrics.ts`:

```ts
/**
* Time in seconds the event should be persisted for.
*/
timeout?: number;

/**
* `Date.now()` when the fragment was last updated.
*/
lastUpdated?: number;
```

And `lastUpdated` is written with `Date.now()` when fragments are created/updated.

Because `/` has higher precedence than `-`, the current expression is evaluated as:

```ts
Date.now() - (fragment.lastUpdated / 1000)
```

not:

```ts
(Date.now() - fragment.lastUpdated) / 1000
```

So any fragment with both `timeout` and `lastUpdated` would become eligible for abandonment much earlier than intended.

I think the check should be one of these instead:

```ts
Date.now() - fragment.lastUpdated > fragment.timeout * 1000
```

or

```ts
(Date.now() - fragment.lastUpdated) / 1000 > fragment.timeout
```

A bit of history in case it helps:

- introduced with event fragments in commit `b820ef131b` (`Implement event fragments`, PR #12251)
- carried forward through later refactors/migrations including `29c2b136b8`, `317d2ef12e`, and `6ae02e8e8a`

I didn’t find a current in-tree caller that sets `timeout`, so this may be latent today rather than something widely hit in production, but the timeout path itself looks incorrect as implemented.

Read the timeout check in app/scripts/controllers/metametrics-controller.ts alongside the fragment contract in shared/constants/metametrics.ts. Confirm how timeout and lastUpdated units are represented, then verify that the abandonment check compares elapsed time using matching units. Done means the check no longer treats a millisecond timestamp as seconds and preserves the documented timeout behavior.

Written by the indexing model from the issue text.