Fix library name (#722)

Author: alexandersazonof

website/pages/en/operating-graph-node.mdx

@@ -45,7 +45,7 @@ To enable monitoring and reporting, Graph Node can optionally log metrics to a P
 - **Additional Requirements for Ubuntu users** - To run a Graph Node on Ubuntu a few additional packages may be needed.
 
 ```sh
-sudo apt-get install -y clang libpg-dev libssl-dev pkg-config
+sudo apt-get install -y clang libpq-dev libssl-dev pkg-config
 ```
 
 #### Setup