doc/manuals: Use correct path (osmo-remsim-doc)

Change-Id: I16a56af66a450e6bb19a53c652d6f93d35aacb8e
diff --git a/doc/manuals/Makefile.am b/doc/manuals/Makefile.am
index 36ca4f2..59ec86d 100644
--- a/doc/manuals/Makefile.am
+++ b/doc/manuals/Makefile.am
@@ -8,5 +8,6 @@
   include $(OSMO_GSM_MANUALS_DIR)/build/Makefile.asciidoc.inc
   osmo-remsim-usermanual.pdf: $(srcdir)/chapters/*.adoc
 
+  OSMO_REPOSITORY = osmo-remsim
   include $(OSMO_GSM_MANUALS_DIR)/build/Makefile.common.inc
 endif