Only downgrade sections and subsections

Fix issue with last commit

Makefile

@@ -61,7 +61,8 @@ $(1).tex: $(1).ipynb
 	sed \
 	-e '/\\documentclass/,/\\maketitle/d' \
 	-e '/\\end{document}/d' \
-	-e 's;section{;subsection{;' \
+	-e 's;\\subsection;\\subsubsection;' \
+	-e 's;\\section;\\subsection;' \
 	-i  $(1).tex
 endef