roles/ipareplica/README: _http_cert_files and _pkinit_cert_files are lists

In the README these settings have been single values instead of string
lists:
  ipareplica_http_cert_file
  ipareplica_pkinit_cert_file
instead of
  ipareplica_http_cert_files
  ipareplica_pkinit_cert_files

roles/ipareplica/README.md

@@ -162,8 +162,8 @@ SSL certificate Variables
 Variable | Description | Required
 -------- | ----------- | --------
 `ipareplica_dirsrv_cert_files` | Files containing the Directory Server SSL certificate and private keys. (list of strings) | no
-`ipareplica_http_cert_file` | File containing the Apache Server SSL certificate and private key. (string) | no
-`ipareplica_pkinit_cert_file` | File containing the Kerberos KDC SSL certificate and private key. (string) | no
+`ipareplica_http_cert_files` | Files containing the Apache Server SSL certificate and private key. (list of string) | no
+`ipareplica_pkinit_cert_files` | Files containing the Kerberos KDC SSL certificate and private key. (list of string) | no
 `ipareplica_dirsrv_pin` | The password to unlock the Directory Server private key. (string) | no
 `ipareplica_http_pin` | The password to unlock the Apache Server private key. (string) | no
 `ipareplica_pkinit_pin` | The password to unlock the Kerberos KDC private key. (string) | no