[Doc] Bug fix in readthedoc setting

.readthedocs.yml

@@ -1,8 +1,20 @@
-- name: en
-  base: DOC/
-  type: sphinx
-  formats:
-      html: true
-      pdf: true
-  python:
-      setup_install: true
+# .readthedocs.yml
+# Read the Docs configuration file
+# See https://docs.readthedocs.io/en/stable/config-file/v2.html for details
+
+# Required configuration file version
+version: 2
+
+# Build documentation in the docs/ directory with Sphinx
+sphinx:
+  builder: dirhtml
+  configuration: DOC/source/conf.py
+
+# Optionally build your docs in additional formats such as PDF and ePub
+formats: all
+
+# Optionally set the version of Python and requirements required to build your docs
+python:
+  version: 3.7
+  install:
+    - requirements: DOC/requirements.txt