USE_GCC=7 is the oldest version supported, so change that into the

preferred USE_GCC=yes.

This should not practically affect most systems and builds since, unless
GCC 7 is the only one installed, we'd go for the default version anyway.

Approved by:	portmgr (blanket)

www/trafficserver/Makefile

@@ -26,7 +26,7 @@ USES=		compiler:c++17-lang cpe gmake libtool ncurses pathfix \
 
 CPE_VENDOR=	apache
 CPE_PRODUCT=	traffic_server
-USE_GCC=	7+
+USE_GCC=	yes
 USE_PERL5=	build run
 USE_LDCONFIG=	yes
 USE_RC_SUBR=	${PORTNAME}