Add sphinxcontirb.spelling extension into conf.py

- It also align dmi module with cps for tox.ini config

Issue-ID: DOC-798
Change-Id: Ie241f5490243de43fa2889ef88a6dca93702f7a9
Signed-off-by: halil.cakal <halil.cakal@est.tech>
diff --git a/docs/tox.ini b/docs/tox.ini
index dc46706..ea1c195 100644
--- a/docs/tox.ini
+++ b/docs/tox.ini
@@ -43,4 +43,4 @@
     -chttps://raw.githubusercontent.com/openstack/requirements/stable/yoga/upper-constraints.txt
     -chttps://git.onap.org/doc/plain/etc/upper-constraints.onap.txt?h=master
 commands =
-    sphinx-build -W -q -b spelling -Dextensions=sphinxcontrib.spelling -d {envtmpdir}/doctrees {toxinidir} {toxinidir}/_build/spellcheck
+    sphinx-build -b spelling -d {envtmpdir}/doctrees {toxinidir} {toxinidir}/_build/spellcheck