[Issue #149] documentation update

Author: gsmolk

doc/pgprobackup.xml

@@ -3609,7 +3609,6 @@ pg_probackup restore -B <replaceable>backup_dir</replaceable> --instance <replac
 [-R | --restore-as-replica] [--no-validate] [--skip-block-validation]
 [--force] [--no-sync]
 [--restore-command=<replaceable>cmdline</replaceable>]
-[--restore-command=<replaceable>cmdline</replaceable>]
 [--primary-conninfo=<replaceable>primary_conninfo</replaceable>]
 [-S | --primary-slot-name=<replaceable>slotname</replaceable>]
 [<replaceable>recovery_target_options</replaceable>] [<replaceable>logging_options</replaceable>] [<replaceable>remote_options</replaceable>]