Fix Sphinx nitpicky warnings in ftplib.rst

Replace :meth:`makepasv` references (undocumented method) with plain
prose to avoid unresolved cross-reference warnings in nitpicky mode.

Author: simonepelosi

Doc/library/ftplib.rst

@@ -278,14 +278,14 @@ FTP objects
 
    .. attribute:: FTP.prefer_epsv
 
-      A :class:`bool` that controls whether :meth:`makepasv` tries the EPSV
-      command (RFC 2428) before falling back to PASV on IPv4 connections.
-      Defaults to ``True``.
-
-      EPSV responses contain only a port number and no IP address, making them
-      transparent to firewall FTP Application Layer Gateways (ALGs) that
-      commonly intercept and mangle PASV responses.  If the server does not
-      support EPSV, :meth:`makepasv` falls back to PASV automatically.
+       A :class:`bool` that controls whether passive mode data connections
+       try the EPSV command (:rfc:`2428`) before falling back to PASV on IPv4
+       connections.  Defaults to ``True``.
+
+       EPSV responses contain only a port number and no IP address, making them
+       transparent to firewall FTP Application Layer Gateways (ALGs) that
+       commonly intercept and mangle PASV responses.  If the server does not
+       support EPSV, the connection falls back to PASV automatically.
 
       Set to ``False`` to restore the legacy PASV-first behavior on IPv4.