adding global constraints

otc_metadata/templates/tox.ini.j2

@@ -24,7 +24,9 @@ commands = {posargs}
 # This env is invoked in the periodic pipeline and is therefore responsible to
 # build all relevant docs at once.
 [testenv:docs]
-deps = -r{toxinidir}/doc/requirements.txt
+deps =
+  -r{toxinidir}/doc/requirements.txt
+  -c https://raw.githubusercontent.com/opentelekomcloud-docs-swiss/docs-constraints/main/constraints.txt
 allowlist_externals =
   mkdir
   cp
@@ -59,7 +61,6 @@ commands =
 {% set loc = doc.rst_location | replace('/source', '') %}
 # HTML version
 [testenv:{{ doc.type }}]
-deps = -r{toxinidir}/doc/requirements.txt
 allowlist_externals =
   cp
   mkdir
@@ -78,7 +79,6 @@ commands =
 
 # Json version (for search)
 [testenv:json-{{ doc.type }}]
-deps = -r{toxinidir}/doc/requirements.txt
 allowlist_externals =
   cp
   mkdir