Remove duplicate .readthedocs.yml, fix Sphinx warning (horovod#3367)

Signed-off-by: Enrico Minack <github@enrico.minack.dev>

.readthedocs.yaml

@@ -1,19 +1,33 @@
-# .readthedocs.yaml
-# Read the Docs configuration file
+# Copyright (c) 2019 Uber Technologies, Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+# ==============================================================================
+#
+# ReadTheDocs.io build configuration: supply addition pip install options
 # See https://docs.readthedocs.io/en/stable/config-file/v2.html for details
-
-# Required
+#
 version: 2
 
 # Build documentation in the docs/ directory with Sphinx
 sphinx:
-   configuration: docs/conf.py
+  configuration: docs/conf.py
+  fail_on_warning: true
 
-# Optionally build your docs in additional formats such as PDF
+# Don't build any extra formats
 formats: []
 
-# Optionally set the version of Python and requirements required to build your docs
+# Requirements for building docs
 python:
-   version: 3.7
-   install:
-   - requirements: docs/requirements.txt
+  version: 3.7
+  install:
+    - requirements: docs/requirements.txt

horovod/ray/elastic.py

@@ -179,6 +179,7 @@ class ElasticRayExecutor:
             settings, use_gpu=True, cpus_per_slot=2)
         executor.start()
         executor.run(train_fn)
+
     warning:: .. deprecated:: 0.25.0
     """