fix(AlarmFactory): Fix wording for actionsSuppressorExtensionPeriod prop to use 'duration' instead of 'time in seconds'

[jonathan-luo]

Description

No code logic changes.

Unfortunately missed changing actionsSuppressorExtensionPeriod prop description to use "duration" instead of "time in seconds". The "time in seconds" descriptor is used in CloudFormation documentation, but since the prop type required by CDK CompositeAlarm is Duration, it's more accurate to use "duration" (and to be consistent with the CDK Composite Alarm definition).

Note: This wording change was already done for actionsSuppressorWaitPeriod; only actionsSuppressorExtensionPeriod was missed.

Testing

• yarn build -- no code logic changes so no additional unit tests necessary.

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[jonathan-luo]

Initial build failed since updated API.md was not included in commit. Have fixed that now.