doc: Stop generating the modules index

We still have a few unused artifacts in the docs generation,
this is just one less.

doc/Makefile

@@ -64,7 +64,7 @@ all: html devhelp
 templates:
 	mkdir -p source/elements
 	mkdir -p source/sources
-	$(SPHINXAPIDOC) --force --separate --module-first --no-headings -o source $(CURDIR)/../buildstream
+	$(SPHINXAPIDOC) --force --separate --module-first --no-headings --no-toc -o source $(CURDIR)/../buildstream
 	$(call plugin-doc-skeleton,$(CURDIR)/../buildstream/plugins/elements,elements)
 	$(call plugin-doc-skeleton,$(CURDIR)/../buildstream/plugins/sources,sources)
 

doc/source/main_core.rst

@@ -22,4 +22,4 @@ other more elaborate details about BuildStream internals.
 .. toctree::
    :hidden:
 
-   modules
+   buildstream