DOC: quic: Wrong syntax for "quic-cc-algo" keyword.

As the argument to "quic-cc-algo" is mandatory, brackets must be used here
in the documentation.

Must be backported as far as 2.6.

(cherry picked from commit d9bf1b6c413d18cd7ab462842b3b32fff7fc8a39)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
diff --git a/doc/configuration.txt b/doc/configuration.txt
index 56dc184..627def8 100644
--- a/doc/configuration.txt
+++ b/doc/configuration.txt
@@ -15437,7 +15437,7 @@
   instance, it is possible to force the http/2 on clear TCP by specifying "proto
   h2" on the bind line.
 
-quic-cc-algo [ cubic | newreno ]
+quic-cc-algo { cubic | newreno }
   This is a QUIC specific setting to select the congestion control algorithm
   for any connection attempts to the configured QUIC listeners. They are similar
   to those used by TCP.