Remove parallel building of Sphinx documentation.

Since version 1.0.0 of the sphinxcontrib-bibtex extension, parallel
building of the Sphinx documentation emits a warning (and thus makes
our warning-free build fail).

This change was already done in Makefile.doc as part of #11732.

1 files changed, 1 insertions, 1 deletions

diff --git a/doc/dune b/doc/dune
index 3a8efbb36d..02ca33b682 100644
--- a/doc/dune
+++ b/doc/dune
@@ -14,7 +14,7 @@
   unreleased.rst
   (env_var SPHINXWARNOPT))
  (action
-  (run env COQLIB=%{project_root} sphinx-build -j4 %{env:SPHINXWARNOPT=-W} -b html -d sphinx_build/doctrees sphinx sphinx_build/html)))
+  (run env COQLIB=%{project_root} sphinx-build %{env:SPHINXWARNOPT=-W} -b html -d sphinx_build/doctrees sphinx sphinx_build/html)))
 
 (alias
  (name refman-html)