[OOM] Add sphinx_toolbox for OOM

Signed-off-by: efiacor <fiachra.corcoran@est.tech>
Change-Id: Ie070ece8c9b0b5c84fe59c3499daa286d36b174e
Issue-ID: OOM-3028
diff --git a/etc/upper-constraints.onap.txt b/etc/upper-constraints.onap.txt
index 1913e6c..60a33d2 100644
--- a/etc/upper-constraints.onap.txt
+++ b/etc/upper-constraints.onap.txt
@@ -1,6 +1,7 @@
 lfdocs-conf===0.8.0
 sphinxcontrib-needs===0.7.9
 sphinxcontrib.plantuml===0.24
+sphinx_toolbox==3.2.0
 sphinxcontrib.nwdiag===2.0.0
 sphinxcontrib-swaggerdoc===0.1.7
 sphinx-rtd-theme===1.0.0