How to remove the blank line at the end of a tcolorbox?

I have the following LaTeX code:

\documentclass[11pt]{book}
\usepackage[default]{opensans}
\usepackage{alltt}
\usepackage[listings]{tcolorbox}
\usepackage{xcolor}

\newenvironment{generalSrcCode}
  {\vspace{5pt}
   \begin{tcolorbox}[
   colback=lightgray,
   coltext=black,
   boxrule=0pt,
   arc=5pt,
   before skip=5pt,
   after skip=5pt,
   left=5pt,
   right=5pt,
   top=5pt,
   bottom=5pt,
   boxsep=0pt,
   valign=center,
   baseline = 0pt
  ]\begin{alltt}\color{black}\ignorespaces}
  {\end{alltt}\end{tcolorbox}
   \vspace{5pt}
 }

 \begin{document}
 \noindent
Run the following commands in a terminal:
\begin{generalSrcCode}
sudo apt install -y postgresql-common
sudo /usr/share/postgresql-common/pgdg/apt.postgresql.org.sh
\end{generalSrcCode}
\noindent
Once you have run the above-mentioned commands, 
\end{document}

As you can see, there is a blank line at the end of the second command in the tcolorbox. I want to get rid of it and also center the content in the box vertically. Is this possible?

Thanks in advance

As you are anyway using a tcolorbox around the code, I would directly use a tcblisting:

\documentclass[11pt]{book}
\usepackage[default]{opensans}
\usepackage{alltt}
\usepackage[listings]{tcolorbox}
\usepackage{xcolor}

\NewTCBListing{generalSrcCode}{}{
   colback=lightgray,
   coltext=black,
   boxrule=0pt,
   arc=5pt,
   before skip=5pt,
   after skip=5pt,
   left=5pt,
   right=5pt,
   top=5pt,
   bottom=5pt,
   boxsep=0pt,
   valign=center,
   baseline = 0pt,
   listing only
}

 \begin{document}
 \noindent
Run the following commands in a terminal:
\begin{generalSrcCode}
sudo apt install -y postgresql-common
sudo /usr/share/postgresql-common/pgdg/apt.postgresql.org.sh
\end{generalSrcCode}
\noindent
Once you have run the above-mentioned commands, 
\end{document}