Use zuul-sphinx README.rst detection

With the dependent change, zuul-sphinx will raise a warning when the
autoroles matcher finds a role without a README.rst.  Since we
error-on-warnings this will stop the docs build.  Thus we don't need
this explicit linters check.

Change-Id: I02eefce2448152505bacba3b2a12021515b4a31a
Depends-On: https://review.openstack.org/596014

tools/check_readme.sh

@@ -1,9 +0,0 @@
-#!/bin/bash
-
-# Trivial script run from tox -e linters to ensure roles have a
-# README.rst attached
-
-if ! [ -f $1/README.rst ]; then
-    echo "*** Missing role documentation: $1/README.rst"
-    exit 1
-fi

tox.ini

@@ -12,8 +12,6 @@ deps = -r{toxinidir}/test-requirements.txt
 [testenv:linters]
 whitelist_externals = bash
 commands =
-  bash -c "find roles/ playbooks/roles -maxdepth 1 -mindepth 1 -type d -print0 | \
-     xargs -t -n1 -0 {toxinidir}/tools/check_readme.sh"
   flake8
   {toxinidir}/tools/run-bashate.sh
   python3 {toxinidir}/tools/sorted_modules_env.py {toxinidir}/modules.env