Fix docs requirements

It was linked to molecule requirements because we were lazy. We don't
need to install molecule when generating docs.

Change-Id: I108f8b48be09c56c3c74d81780ca1c035a611962
Closes-Bug: #1949211

doc/requirements.txt

@@ -1 +0,0 @@
-../molecule-requirements.txt

doc/requirements.txt

@@ -0,0 +1,10 @@
+# this is required for the docs build jobs
+ansible-core<2.12.0
+sphinx>=2.0.0,!=2.1.0 # BSD
+openstackdocstheme>=2.2.1 # Apache-2.0
+reno>=3.1.0 # Apache-2.0
+doc8>=0.8.1 # Apache-2.0
+bashate>=0.6.0 # Apache-2.0
+metalsmith>=1.4.0 # Apache-2.0
+jsonschema  # MIT
+ruamel.yaml

molecule-requirements.txt

@@ -15,15 +15,7 @@ testinfra
 netaddr
 jinja2
 
-# this is required for the docs build jobs
 ansible-core<2.12.0
-sphinx>=2.0.0,!=2.1.0 # BSD
-openstackdocstheme>=2.2.1 # Apache-2.0
-reno>=3.1.0 # Apache-2.0
-doc8>=0.8.1 # Apache-2.0
-bashate>=0.6.0 # Apache-2.0
-metalsmith>=1.4.0 # Apache-2.0
-jsonschema  # MIT
 
 # Upstream requirements from constraints.txt
 tripleo-common