Make recent RHEL releases more prominent and remove remaining RHEL 6 …

…stuff

templates/pages/download/linux/redhat.html

@@ -72,19 +72,19 @@ <h2>PostgreSQL Yum Repository</h2>
 <h2>Included in Distribution</h2>
 <p>
 These distributions all include PostgreSQL by default. To install
-PostgreSQL from these repositories, use the <var>yum</var> command on RHEL 6 and 7:
+PostgreSQL from these repositories, use the <var>dnf</var> command on RHEL 8 and Fedora:
 </p>
 <p>
 <code>
-yum install postgresql-server
+dnf install postgresql-server
 </code>
 </p>
 <p>
-or <var>dnf</var> command on RHEL 8 and Fedora:
+or <var>yum</var> command on RHEL / CentOS 7:
 </p>
 <p>
 <code>
-dnf install postgresql-server
+yum install postgresql-server
 </code>
 </p>
 <p>