Fix RHEL/CentOS install docs

README.md

@@ -184,7 +184,7 @@ You can use [pacman](https://www.archlinux.org/pacman/) to install the packages.
     Download the Linux package from the [latest `step-ca` release](https://github.com/smallstep/certificates/releases/latest):
 
     ```
-    $ wget -O step-ca.tar.gz https://github.com/smallstep/cli/releases/download/vX.Y.Z/step_linux_X.Y.Z_amd64.tar.gz
+    $ wget -O step-ca.tar.gz https://github.com/smallstep/certificates/releases/download/vX.Y.Z/step-certificates_linux_X.Y.Z_amd64.tar.gz
     ```
 
     Install `step-ca` by unzipping and copying the executable over to `/usr/bin`: