Use archive yum repos to get PostgreSQL 13

+------------------------------------------------------------------------------+
| THIS COMMIT IS FOR TESTING ONLY. IT SHOULD BE REMOVED WHEN THIS PR IS MERGED |
+------------------------------------------------------------------------------+

Author: GirgerS

doc/xml/user-guide.xml

@@ -390,6 +390,13 @@
         "enabled=1" \
         "gpgcheck=1" \
         "gpgkey=https://yum.postgresql.org/keys/PGDG-RPM-GPG-KEY-RHEL" > /etc/yum.repos.d/pgdg-12.repo
+        RUN printf "%s\n" \
+        "[pgdg13-archive]" \
+        "name=PostgreSQL 13 RPMs for RHEL/Rocky Linux/AlmaLinux 8" \
+        "baseurl=https://yum-archive.postgresql.org/13/redhat/rhel-8-x86_64" \
+        "enabled=1" \
+        "gpgcheck=1" \
+        "gpgkey=https://yum.postgresql.org/keys/PGDG-RPM-GPG-KEY-RHEL" > /etc/yum.repos.d/pgdg-13.repo