Update ipa-replica-install documentation

Update the ipa-replica-install man page and help to reflect that replica_file
is optional instead of mandatory.

https://fedorahosted.org/freeipa/ticket/6164

Reviewed-By: Martin Basti <mbasti@redhat.com>

install/tools/ipa-replica-install

@@ -27,7 +27,7 @@ ReplicaInstall = cli.install_tool(
     Replica,
     command_name='ipa-replica-install',
     positional_arguments=['replica_file'],
-    usage='%prog [options] REPLICA_FILE',
+    usage='%prog [options] [REPLICA_FILE]',
     log_file_name=paths.IPAREPLICA_INSTALL_LOG,
     debug_option=True,
 )

install/tools/man/ipa-replica-install.1

@@ -22,7 +22,7 @@ ipa\-replica\-install \- Create an IPA replica
 .SH "SYNOPSIS"
 .SS "DOMAIN LEVEL 0"
 .TP
-ipa\-replica\-install [\fIOPTION\fR]... replica_file
+ipa\-replica\-install [\fIOPTION\fR]... [replica_file]
 .SS "DOMAIN LEVEL 1"
 .TP
 ipa\-replica\-install [\fIOPTION\fR]...