email: Removed unnecessary forward declaration

Due to the reordering of functions in commit 586f5d3614 the forward
declaration to state_upgrade_tls() are no longer required.

lib/imap.c

@@ -98,7 +98,6 @@ static int imap_getsock(struct connectdata *conn, curl_socket_t *socks,
                         int numsocks);
 static CURLcode imap_doing(struct connectdata *conn, bool *dophase_done);
 static CURLcode imap_setup_connection(struct connectdata *conn);
-static CURLcode imap_state_upgrade_tls(struct connectdata *conn);
 
 /*
  * IMAP protocol handler.

lib/pop3.c

@@ -103,7 +103,6 @@ static int pop3_getsock(struct connectdata *conn, curl_socket_t *socks,
                         int numsocks);
 static CURLcode pop3_doing(struct connectdata *conn, bool *dophase_done);
 static CURLcode pop3_setup_connection(struct connectdata *conn);
-static CURLcode pop3_state_upgrade_tls(struct connectdata *conn);
 
 /*
  * POP3 protocol handler.

lib/smtp.c

@@ -99,7 +99,6 @@ static int smtp_getsock(struct connectdata *conn, curl_socket_t *socks,
                         int numsocks);
 static CURLcode smtp_doing(struct connectdata *conn, bool *dophase_done);
 static CURLcode smtp_setup_connection(struct connectdata *conn);
-static CURLcode smtp_state_upgrade_tls(struct connectdata *conn);
 
 /*
  * SMTP protocol handler.