Update version to 5.0

llvm-svn: 291928
diff --git a/libcxx/docs/conf.py b/libcxx/docs/conf.py
index dee0367..17fb401 100644
--- a/libcxx/docs/conf.py
+++ b/libcxx/docs/conf.py
@@ -47,9 +47,9 @@
 # built documents.
 #
 # The short X.Y version.
-version = '4.0'
+version = '5.0'
 # The full version, including alpha/beta/rc tags.
-release = '4.0'
+release = '5.0'
 
 # The language for content autogenerated by Sphinx. Refer to documentation
 # for a list of supported languages.