biology/ucsc-userapps: Replace dependencies

Currently their is a hardcoded dependency on mysql57-client which is
about to be removed. Ports depending on mysql should always use
USES=mysql rather than hardcoded *_DEPENDS. As I do not have a licensed
version of this application for now switch to USES=mysql. This should
not affect the cluster build at all as this is a RESTRICTED ports.

Approved by:	portmgr (blanket)

biology/ucsc-userapps/Makefile

@@ -22,11 +22,10 @@ ONLY_FOR_ARCHS_REASON=	uses _mm_popcnt_u64() function
 
 BUILD_DEPENDS=	bash:shells/bash
 LIB_DEPENDS=	libiconv.so:converters/libiconv \
-		libmysqlclient.so:databases/mysql57-client \
 		libpng.so:graphics/png
 RUN_DEPENDS=	bash:shells/bash
 
-USES=		gmake localbase:ldflags shebangfix perl5 python ssl tar:tgz
+USES=		gmake localbase:ldflags mysql shebangfix perl5 python ssl tar:tgz
 
 RESTRICTED=	Redistribution is limited, see license