libssh2: remove unused variable from libssh2's struct

Closes #10777

lib/vssh/libssh2.c

@@ -2405,7 +2405,6 @@ static CURLcode ssh_statemach_act(struct Curl_easy *data, bool *block)
       result = Curl_dyn_addf(&sshp->readdir, " -> %s", sshp->readdir_filename);
 
       if(result) {
-        sshc->readdir_line = NULL;
         Curl_safefree(sshp->readdir_filename);
         Curl_safefree(sshp->readdir_longentry);
         state(data, SSH_SFTP_CLOSE);
@@ -3009,12 +3008,9 @@ static CURLcode ssh_statemach_act(struct Curl_easy *data, bool *block)
 
       Curl_safefree(sshc->rsa_pub);
       Curl_safefree(sshc->rsa);
-
       Curl_safefree(sshc->quote_path1);
       Curl_safefree(sshc->quote_path2);
-
       Curl_safefree(sshc->homedir);
-      Curl_safefree(sshc->readdir_line);
 
       /* the code we are about to return */
       result = sshc->actualcode;

lib/vssh/ssh.h

@@ -147,7 +147,6 @@ struct ssh_conn {
 
   char *homedir;              /* when doing SFTP we figure out home dir in the
                                  connect phase */
-  char *readdir_line;
   /* end of READDIR stuff */
 
   int secondCreateDirs;         /* counter use by the code to see if the
@@ -159,6 +158,7 @@ struct ssh_conn {
 #if defined(USE_LIBSSH)
   char *readdir_linkPath;
   size_t readdir_len, readdir_totalLen, readdir_currLen;
+  char *readdir_line;
 /* our variables */
   unsigned kbd_state; /* 0 or 1 */
   ssh_key privkey;