games/{enigma,openspades}: rollback USES=magick for my ports

Roll back pessimization introduced in 45526ec for (my) ports which
need *any* version of imagemagick: switch to USES=magick makes them
needlessly requre *specific* version/flavor which cause conflicts.

games/enigma/Makefile

@@ -14,12 +14,13 @@ LIB_DEPENDS=	libxerces-c.so.3:textproc/xerces-c3 \
 		libpng.so:graphics/png \
 		libenet.so:net/enet \
 		libcurl.so:ftp/curl
+BUILD_DEPENDS=	convert:graphics/ImageMagick6
 
 USE_GITHUB=	yes
 GH_ACCOUNT=	Enigma-Game
 GH_PROJECT=	Enigma
 
-USES=		autoreconf:build gettext gmake iconv localbase magick:6,build pkgconfig sdl
+USES=		autoreconf:build gettext gmake iconv localbase pkgconfig sdl
 GNU_CONFIGURE=	yes
 USE_SDL=	sdl2 image2 mixer2 ttf2
 CONFIGURE_ARGS=	--with-system-enet

games/openspades/Makefile

@@ -15,14 +15,15 @@ LICENSE_FILE=	${WRKSRC}/LICENSE
 ONLY_FOR_ARCHS=	amd64 powerpc64 powerpc64le
 ONLY_FOR_ARCHS_REASON=	bundles non-portable AngelScript
 
+BUILD_DEPENDS=	convert:graphics/ImageMagick6 # for building icons
 LIB_DEPENDS=	libcurl.so:ftp/curl \
 		libopusfile.so:audio/opusfile
 
 USE_GITHUB=	yes
 GH_ACCOUNT=	yvt
 
 USES=		cmake:insource compiler:c++11-lib desktop-file-utils dos2unix \
-		gl gnome magick:6,build openal sdl xorg
+		gl gnome openal sdl xorg
 CMAKE_ARGS=	-DOPENSPADES_RESOURCES=OFF \
 		-DOPENSPADES_INSTALL_MAN="man/man6" \
 		-DOPENSPADES_INSTALL_BINARY="bin" \