doc: remove making image directory

It looks like it is a leftover from the past

Signed-off-by: Adam Wujek <adam.wujek@cern.ch>

doc/Makefile

@@ -39,15 +39,12 @@ RELEASE=$(shell git describe --always --dirty)
 	$(MAKEINFO) --no-headers $< > $@
 
 ##############################################
-.PHONY: all images check terse clean install
+.PHONY: all check terse clean install
 .INTERMEDIATE: $(TEXI)
 
-all: images $(ALL)
+all: $(ALL)
 	$(MAKE) terse
 
-images::
-	if [ -d images ]; then $(MAKE) -C images || exit 1; fi
-
 check: _err.ps
 	gs -sDEVICE=linux -r320x200x16 $<