[COMMON] Remove parallelism in doc linting

`sphinxcontrib.needs` is not safe for parallel work and thus a warning
is set during linting which makes it fail.
We then remove the parallelism for sphinx here.

Issue-ID: OOM-2648
Signed-off-by: Sylvain Desbureaux <sylvain.desbureaux@orange.com>
Change-Id: I820e63fee78578794c96c3ff9867c4ecc56ba50e
diff --git a/tox.ini b/tox.ini
index fa18976..c685a3f 100644
--- a/tox.ini
+++ b/tox.ini
@@ -17,11 +17,11 @@
 [testenv:docs]
 deps = -rdocs/requirements-docs.txt
 commands =
- sphinx-build -j auto -W -b html -n -W -d {envtmpdir}/doctrees ./docs/ {toxinidir}/docs/_build/html
+ sphinx-build -W -b html -n -W -d {envtmpdir}/doctrees ./docs/ {toxinidir}/docs/_build/html
 
 [testenv:docs-linkcheck]
 deps = -rdocs/requirements-docs.txt
-commands = sphinx-build -j auto -W -b linkcheck -d {envtmpdir}/doctrees ./docs/ {toxinidir}/docs/_build/linkcheck
+commands = sphinx-build -W -b linkcheck -d {envtmpdir}/doctrees ./docs/ {toxinidir}/docs/_build/linkcheck
 
 [testenv:gitlint]
 basepython = python3