selinux: remove runtime disable message in the install_policy.sh script

We are in the process of deprecating the runtime disable mechanism,
let's not reference it in the scripts.

Signed-off-by: Paul Moore <[e-mail]>

scripts/selinux/install_policy.sh

···
 if selinuxenabled; then
     echo "SELinux is already enabled"
     echo "This prevents safely relabeling all files."
-    echo "Boot with selinux=0 on the kernel command-line or"
-    echo "SELINUX=disabled in /etc/selinux/config."
+    echo "Boot with selinux=0 on the kernel command-line."
     exit 1
 fi