Removing doctree from generated sources. There is no need to publish it.

Makefile

@@ -57,7 +57,7 @@ clean:
 
 html_all_languages:
 	@echo "Building documentation in html for all languages"
-	set -e; for lang in "en" "es" "fr" "ge" "it" "ko" "nl" "cz" "ca" "fi" "is"; do echo "Building language $$lang"  && make html -e SPHINXOPTS="-D language='$$lang'" -e "BUILDDIR='target/doc/$$lang'"; done
+	set -e; for lang in "en" "es" "fr" "ge" "it" "ko" "nl" "cz" "ca" "fi" "is"; do echo "Building language $$lang"  && make html -e SPHINXOPTS="-D language='$$lang'" -e "BUILDDIR='target/doc/$$lang' -d $(BUILDDIR)/doctrees"; done
 
 update_translations:
 	@echo "Pushing strings to transifex"