Revert "Redmine #7139: Add documentation for package module API."

This reverts commit f0d9bbb.

The documentation has moved to the documentation repository instead.

Makefile.am

@@ -10,12 +10,7 @@ endif
 nobase_dist_masterfiles_DATA = @MASTERFILES_INSTALL_TARGETS@
 masterfilesdir=$(datadir)
 
-EXTRA_DIST = CONTRIBUTING.md \
-	inventory/README.md \
-	lib/README.md \
-	LICENSE \
-	PACKAGE-MODULE-API.md \
-	README.md
+EXTRA_DIST = README.md inventory/README.md lib/README.md CONTRIBUTING.md LICENSE
 
 # Do not reveal usernames of the buildslave
 TAR_OPTIONS = --owner=0 --group=0