Update 2020/ferguson1/Makefile

I forgot to change the cannibalism.log to cannibalism.log.md in the DATA
variable.

2020/ferguson1/Makefile

@@ -113,7 +113,7 @@ ENTRY= ferguson1
 PROG= prog
 #
 OBJ= ${PROG}.o
-DATA= COMPILING.md HACKING.md bugs.html bugs.md cake.jpg cannibalism.log \
+DATA= COMPILING.md HACKING.md bugs.html bugs.md cake.jpg cannibalism.log.md \
 	chocolate-cake.html chocolate-cake.md crazy.log gameplay.html gameplay.md \
 	halfwidth_vs_fullwidth.png ioccc-cake.jpg play.sh prog.2.c prog.3-j.c \
 	prog.3.c snake-colours.sh snake.1 spoilers.html spoilers.md \