Fix bug in https://trac.osgeo.org/grass/changeset/39667 (endif->endef)

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@39707 15284696-431f-4ddb-bdfa-cd5b030d7da7

man/Makefile

@@ -60,7 +60,7 @@ $(HTMLDIR)/index.html:
 define category_rule
 $$(HTMLDIR)/$(2).html: $$(wildcard $$(HTMLDIR)/$(1).*.html)
 	$$(call build,class,$(1) $(2))
-endif
+endef
 
 $(foreach cat,$(categories),$(eval $(call category_rule,$(firstword $(subst :, ,$(cat))),$(lastword $(subst :, ,$(cat))))))