TUN-9919: Make RPM postinstall scriplet idempotent

* TUN-9919: Make RPM postinstall scriplet idempotent

Before this commit the postinstall scriptlet isn't idempotent, meaning the users see this error in their upgrade logs:

`ln: failed to create symbolic link '/usr/local/bin/cloudflared': File exists
warning: %post(cloudflared-2025.10.0-1.x86_64) scriptlet failed, exit status 1`

This doesn't break the upgrade (which is why we haven't touched this in 5 years), but adding the -f (force) flag to the symlink command prevents this issue from happening

Closes TUN-9919

Author: GoncaloGarcia

postinst.sh

@@ -1,5 +1,5 @@
 #!/bin/bash
 set -eu
-ln -s /usr/bin/cloudflared /usr/local/bin/cloudflared
+ln -sf /usr/bin/cloudflared /usr/local/bin/cloudflared
 mkdir -p /usr/local/etc/cloudflared/
 touch /usr/local/etc/cloudflared/.installedFromPackageManager || true