[ci skip] Prepare 3.1.8 release
diff --git a/user_guide_src/source/conf.py b/user_guide_src/source/conf.py
index e03c316..5536699 100644
--- a/user_guide_src/source/conf.py
+++ b/user_guide_src/source/conf.py
@@ -48,9 +48,9 @@
 # built documents.
 #
 # The short X.Y version.
-version = '3.1.8-dev'
+version = '3.1.8'
 # The full version, including alpha/beta/rc tags.
-release = '3.1.8-dev'
+release = '3.1.8'
 
 # The language for content autogenerated by Sphinx. Refer to documentation
 # for a list of supported languages.