DOC: config: fix error-log-format example
In commit 6f7497616 ("MEDIUM: connection: rename fc_conn_err and
bc_conn_err to fc_err and bc_err"), fc_conn_err became fc_err, so
update this example.
diff --git a/doc/configuration.txt b/doc/configuration.txt
index c810fa9..b1fbd64 100644
--- a/doc/configuration.txt
+++ b/doc/configuration.txt
@@ -21409,7 +21409,7 @@
regular traffic log (see option httplog or option httpslog).
# detailed frontend connection error log
- error-log-format "%ci:%cp [%tr] %ft %ac/%fc %[fc_conn_err]/\
+ error-log-format "%ci:%cp [%tr] %ft %ac/%fc %[fc_err]/\
%[ssl_fc_err,hex]/%[ssl_c_err]/%[ssl_c_ca_err]/%[ssl_fc_is_resumed] \
%[ssl_fc_sni]/%sslv/%sslc"