Add bounds to sphinx requirement

As ONAP was created before Oct 20 2020 in RTD, we
must set bounds to enforce a compatible Sphinx version
(see manual).

It also fixes all false concrete dependencies.

Issue-ID: DOC-782

Signed-off-by: Cédric Ollivier <cedric.ollivier@orange.com>
Change-Id: Ie04403c3cdd407823c533aee85f566cf222dd8a5
diff --git a/docs/requirements-docs.txt b/docs/requirements-docs.txt
index edffc4b..3b3441a 100644
--- a/docs/requirements-docs.txt
+++ b/docs/requirements-docs.txt
@@ -1,9 +1,3 @@
-lfdocs-conf~=0.7.5
-funcparserlib~=1.0.0a0
-sphinxcontrib.blockdiag~=2.0.0
-sphinxcontrib-needs<0.6.0
-sphinxcontrib.plantuml~=0.21
-sphinxcontrib.nwdiag~=2.0.0
-sphinxcontrib-seqdiag~=2.0.0
-sphinxcontrib-swaggerdoc~=0.1.7
-sphinx-rtd-theme~=1.0.0
+lfdocs-conf
+sphinx>=4.2.0  # BSD
+sphinx-rtd-theme>=1.0.0  # MIT
diff --git a/docs/tox.ini b/docs/tox.ini
index edac8c3..42ffa68 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
+    -chttps://git.onap.org/doc/plain/etc/upper-constraints.onap.txt
 commands =
     sphinx-build -b html -n -d {envtmpdir}/doctrees ./ {toxinidir}/_build/html
     echo "Generated docs available in {toxinidir}/_build/html"