net/vnstat: Update to 2.11

Changes:	https://github.com/vergoh/vnstat/releases
		https://humdi.net/vnstat/CHANGES

net/vnstat/Makefile

 PORTNAME=	vnstat
-PORTVERSION=	2.10
+PORTVERSION=	2.11
 CATEGORIES=	net
 MASTER_SITES=	https://github.com/vergoh/vnstat/releases/download/v${PORTVERSION}/ \
 		https://humdi.net/vnstat/

net/vnstat/distinfo

-TIMESTAMP = 1669057559
-SHA256 (vnstat-2.10.tar.gz) = a9c61744e5cd8c366e2db4d282badc74021ddb614bd65b41240937997e457d25
-SIZE (vnstat-2.10.tar.gz) = 304464
+TIMESTAMP = 1692812380
+SHA256 (vnstat-2.11.tar.gz) = babc3f1583cc40e4e8ffb2f53296d93d308cb5a5043e85054f6eaf7b4ae57856
+SIZE (vnstat-2.11.tar.gz) = 312821