Drop duplicated doc requirements

Use the single requirements file to maintain requirements to build
documentation.

Also use documentation requirements to build api-ref.

Change-Id: I4df315e5657fc69d3b15bceab0e44191e27e343a

doc/requirements.txt

@@ -6,6 +6,7 @@
 # added in alphabetical order, however, some dependencies may need to
 # be installed in a specific order.
 openstackdocstheme>=2.2.1 # Apache-2.0
+os-api-ref>=1.4.0 # Apache-2.0
 reno>=3.1.0 # Apache-2.0
 sphinx>=2.0.0,!=2.1.0 # BSD
 sphinxcontrib-svg2pdfconverter>=0.1.0 # BSD

test-requirements.txt

@@ -12,7 +12,3 @@ astroid==1.6.5 # LGPLv2.1
 pylint==1.9.2 # GPLv2
 oslotest>=3.2.0 # Apache-2.0
 tenacity>=4.9.0  # Apache-2.0
-# Docs building
-openstackdocstheme>=2.2.1 # Apache-2.0
-os-api-ref>=1.4.0 # Apache-2.0
-reno>=3.1.0 # Apache-2.0

tox.ini

@@ -28,6 +28,7 @@ allowlist_externals = find
 deps =
   -c{env:TOX_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
   -r{toxinidir}/test-requirements.txt
+  -r{toxinidir}/doc/requirements.txt
 commands =
     flake8
     reno lint
@@ -83,6 +84,9 @@ paths = ./trove/hacking
 [testenv:api-ref]
 # This environment is called from CI scripts to test and publish
 # the API Ref to developer.openstack.org.
+deps =
+    -c{env:TOX_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
+    -r{toxinidir}/doc/requirements.txt
 commands =
   rm -rf api-ref/build
   sphinx-build -W -b html -d api-ref/build/doctrees api-ref/source api-ref/build/html
@@ -114,6 +118,10 @@ deps = -r{toxinidir}/requirements.txt
 commands = python tools/trove-pylint.py {posargs:check}
 
 [testenv:docs]
+deps =
+    -c{env:TOX_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
+    -r{toxinidir}/requirements.txt
+    -r{toxinidir}/doc/requirements.txt
 commands = sphinx-build -W -b html doc/source doc/build/html
 
 [testenv:trovestack]