Correct postgresql installation steps

What does this MR do?

This MR corrects the steps to install postgresql when installing via source, on Ubuntu 18.4 and earlier versions, specifically, the following line:

   RELEASE=$(lsb_release -cs) echo "deb http://apt.postgresql.org/pub/repos/apt/ ${RELEASE}"-pgdg main | sudo tee  /etc/apt/sources.list.d/pgdg.list

This command does not set register the correct repository, the RELEASE variable is never set and the following error is thrown on the next step:

The repository 'http://apt.postgresql.org/pub/repos/apt -pgdg Release' does not have a Release file.

The solution is to first execute RELEASE=$(lsb_release -cs) in its own line to set the variable, and then run the rest of the command in a new line.

Related issues

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