Bump docs version to 6.0

llvm-svn: 308466
diff --git a/clang/docs/conf.py b/clang/docs/conf.py
index a9861cd..a12f99a 100644
--- a/clang/docs/conf.py
+++ b/clang/docs/conf.py
@@ -49,9 +49,9 @@
 # built documents.
 #
 # The short version.
-version = '5'
+version = '6'
 # The full version, including alpha/beta/rc tags.
-release = '5'
+release = '6'
 
 # The language for content autogenerated by Sphinx. Refer to documentation
 # for a list of supported languages.