Clears out state persisted reply cache

@alias cleanup

When filling out a reply to a comment,
the text is saved in `localStorage` to
prevent it from disappearing on accidental
page refreshes, browser closes, or navigation.
However, we don't want to pre-fill a comment
reply if the saved version is older than a
certain period of time: in this case, one day.

@returns {undefined}
function cleanupRepliesCache() {
	const keysToRemove = [];

	try {
		for ( let i = 0; i < localStorage.length; i++ ) {
			const storedReplyKey = localStorage.key( i );

			// cleanup caches replies older than a day
			if ( 'reply_' == localStorage.key( i ).substring( 0, 6 ) ) {
				const storedReply = getItem( storedReplyKey );

				if ( storedReply && Date.now() - storedReply[ 1 ] >= 24 * 60 * 60 * 1000 ) {
					keysToRemove.push( storedReplyKey );
				}
			}
		}
	} catch ( e ) {
		debug( 'couldnt cleanup cache' );
	}

	keysToRemove.forEach( function( key ) {
		removeItem( key );
	} );
}