build: Remove test-functions.sh which was moved and renamed

Fixes: commit fca1778

Author: rwmjones

Makefile.am

@@ -93,7 +93,6 @@ EXTRA_DIST = \
 	lib/guestfs-internal-all.h \
 	m4/.gitignore \
 	podcheck.pl \
-	test-functions.sh \
 	tmp/.gitignore \
 	valgrind-suppressions