function getInactivityReasonMessage({ replacedBy }) {
	if (typeof replacedBy === "undefined") {
		return "This feature has been abandoned.";
	}

	if (typeof replacedBy === "string") {
		return `This flag has been renamed '${replacedBy}' to reflect its stabilization. Please use '${replacedBy}' instead.`;
	}

	// null
	return "This feature is now enabled by default.";
}
Creates a message that describes the reason the flag is inactive.
@param {InactiveFlagData} inactiveFlagData Data for the inactive flag.
@returns {string} Message describing the reason the flag is inactive.