Update gpg key source for nodejs

as original one caused following error:

    W: GPG error: https://deb.nodesource.com/node_20.x nodistro InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 2F59B5F99B1BE0B4
    E: The repository 'https://deb.nodesource.com/node_20.x nodistro InRelease' is not signed.

Author: kkimurak

Dockerfile

@@ -36,7 +36,7 @@ RUN set -ex && \
  && echo "deb http://ppa.launchpad.net/nginx/stable/ubuntu focal main" >> /etc/apt/sources.list \
  && wget --quiet -O - https://www.postgresql.org/media/keys/ACCC4CF8.asc | apt-key add - \
  && echo 'deb http://apt.postgresql.org/pub/repos/apt/ focal-pgdg main' > /etc/apt/sources.list.d/pgdg.list \
- && wget --quiet -O - https://deb.nodesource.com/gpgkey/nodesource.gpg.key | apt-key add - \
+ && wget --quiet -O - https://deb.nodesource.com/gpgkey/nodesource-repo.gpg.key | apt-key add - \
  && echo 'deb https://deb.nodesource.com/node_20.x nodistro main' > /etc/apt/sources.list.d/nodesource.list \
  && wget --quiet -O - https://dl.yarnpkg.com/debian/pubkey.gpg  | apt-key add - \
  && echo 'deb https://dl.yarnpkg.com/debian/ stable main' > /etc/apt/sources.list.d/yarn.list \