DOC: config: Fix typo in ssl_fc_unique_id description

In ssl_fc_unique_id decription, threre is a reference to the wrong sample
fetch. ssl_bc_unique_id is used instead of ssl_fc_unique_id.

This patch should fix the issue #1449. It may be backported to all
supportted versions.

(cherry picked from commit 15ae22c02cff36579be13c40bac1c37acc60d352)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
diff --git a/doc/configuration.txt b/doc/configuration.txt
index 31f8493..b78981f 100644
--- a/doc/configuration.txt
+++ b/doc/configuration.txt
@@ -18705,7 +18705,7 @@
 ssl_fc_unique_id : binary
   When the incoming connection was made over an SSL/TLS transport layer,
   returns the TLS unique ID as defined in RFC5929 section 3. The unique id
-  can be encoded to base64 using the converter: "ssl_bc_unique_id,base64".
+  can be encoded to base64 using the converter: "ssl_fc_unique_id,base64".
 
 ssl_fc_server_handshake_traffic_secret : string
   Return the SERVER_HANDSHAKE_TRAFFIC_SECRET as an hexadecimal string for the