clarify who starts the remote agent

It was unclear that the user _only_ needs to have borg installed on a remote system to use client/server mode. Hopefully this change makes it apparent that the user doesn't start anything on the remote system themselves.

docs/faq.rst

@@ -13,11 +13,11 @@ What is the difference between a repo on an external hard drive vs. repo on a se
 
 If Borg is running in client/server mode, the client uses SSH as a transport to
 talk to the remote agent, which is another Borg process (Borg is installed on
-the server, too). The Borg server is doing storage-related low-level repo
-operations (get, put, commit, check, compact), while the Borg client does the
-high-level stuff: deduplication, encryption, compression, dealing with
-archives, backups, restores, etc., which reduces the amount of data that goes
-over the network.
+the server, too) started automatically by the client. The Borg server is doing
+storage-related low-level repo operations (get, put, commit, check, compact),
+while the Borg client does the high-level stuff: deduplication, encryption,
+compression, dealing with archives, backups, restores, etc., which reduces the
+amount of data that goes over the network.
 
 When Borg is writing to a repo on a locally mounted remote file system, e.g.
 SSHFS, the Borg client only can do file system operations and has no agent