Update minimum nodejs version to 8

Change-Id: Ifc7bde634f5b6331a2e76e1d620eb7a2141f4824
diff --git a/polygerrit-ui/README.md b/polygerrit-ui/README.md
index 32e1953..660f54d 100644
--- a/polygerrit-ui/README.md
+++ b/polygerrit-ui/README.md
@@ -8,7 +8,7 @@
 
 ## Installing [Node.js](https://nodejs.org/en/download/) and npm packages
 
-The minimum nodejs version supported is 6.x+
+The minimum nodejs version supported is 8.x+
 
 ```sh
 # Debian experimental