conf: don't fail on `server_password_command`

Don't fail when parsing an IMAP config when it has
`server_password_command` set.

Closes #139

Meli stopped recognizing server_password_command configuration #139

melib/src/backends/imap.rs

@@ -1549,6 +1549,7 @@ impl ImapType {
                 s.name.as_str(),
             )));
         }
+        let _ = get_conf_val!(s["server_password_command"]);
         get_conf_val!(s["server_port"], 143)?;
         let use_tls = get_conf_val!(s["use_tls"], true)?;
         let use_starttls = get_conf_val!(s["use_starttls"], false)?;

melib/src/backends/nntp.rs

@@ -696,6 +696,7 @@ impl NntpType {
                 s.name.as_str(),
             )));
         }
+        let _ = get_conf_val!(s["server_password_command"]);
         let server_port = get_conf_val!(s["server_port"], 119)?;
         let use_tls = get_conf_val!(s["use_tls"], server_port == 563)?;
         let use_starttls = get_conf_val!(s["use_starttls"], !(server_port == 563))?;