docs(ecs): fix incorrect rate (#32796)

`rate(1 min)` should be `rate(1 minute)`

See: https://docs.aws.amazon.com/eventbridge/latest/userguide/eb-scheduled-rule-pattern.html#eb-rate-expressions

### Issue # (if applicable)

Closes #<issue number here>.

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### Checklist
- [ ] My code adheres to the [CONTRIBUTING GUIDE](https://github.com/aws/aws-cdk/blob/main/CONTRIBUTING.md) and [DESIGN GUIDELINES](https://github.com/aws/aws-cdk/blob/main/docs/DESIGN_GUIDELINES.md)

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packages/aws-cdk-lib/aws-ecs/README.md

@@ -1180,7 +1180,7 @@ taskDefinition.addContainer('TheContainer', {
 
 // An Rule that describes the event trigger (in this case a scheduled run)
 const rule = new events.Rule(this, 'Rule', {
-  schedule: events.Schedule.expression('rate(1 min)'),
+  schedule: events.Schedule.expression('rate(1 minute)'),
 });
 
 // Pass an environment variable to the container 'TheContainer' in the task