astro/josm: update java version requirement

astro/josm/Makefile

 PORTNAME=	josm
 PORTVERSION=	19128
+PORTREVISION=	1
 CATEGORIES=	astro java
 MASTER_SITES=	https://josm.openstreetmap.de/download/
 DISTNAME=	${PORTNAME}-snapshot-${PORTVERSION}.jar
@@ -17,7 +18,7 @@ NO_WRKSUBDIR=	yes
 
 USES=		zip:infozip
 USE_JAVA=	yes
-JAVA_VERSION=	8+
+JAVA_VERSION=	11+
 
 NO_BUILD=	yes
 NO_ARCH=	yes