Leverage upper-constraints files to pin all dependencies

It leverages the latest change from lfdocs-conf and the
upper-constraints.txt now centralized in ONAP docs.
In a long run, upperconstraints.os.txt should be removed once ONAP
is synced with OpenStack.

It removes tox and setuptools from requirements as nothing depends on them
(most requirements should be removed except lfdocsconf)

Issue-ID: DOC-765

Signed-off-by: Cédric Ollivier <cedric.ollivier@orange.com>
Change-Id: If2b56476e9dad97b692a4e5143b15efc1a7787c3
(cherry picked from commit 8c23c98c827c95615e745e5a4860583f368e5eab)
diff --git a/docs/tox.ini b/docs/tox.ini
index edac8c3..bf9bc51 100644
--- a/docs/tox.ini
+++ b/docs/tox.ini
@@ -5,7 +5,10 @@
 
 [testenv:docs]
 basepython = python3
-deps = -r{toxinidir}/requirements-docs.txt
+deps =
+    -r{toxinidir}/requirements-docs.txt
+    -chttps://git.onap.org/doc/plain/etc/upper-constraints.os.txt?h=istanbul
+    -chttps://git.onap.org/doc/plain/etc/upper-constraints.onap.txt?h=istanbul
 commands =
     sphinx-build -b html -n -d {envtmpdir}/doctrees ./ {toxinidir}/_build/html
     echo "Generated docs available in {toxinidir}/_build/html"