DOC: configuration.txt: do-resolve must use host_only to remove its port.

The do-resolve action does not support a port in its parameter string,
the host_only converter must be used.

Must be backported to 2.6.
diff --git a/doc/configuration.txt b/doc/configuration.txt
index fce5698..24dc9e3 100644
--- a/doc/configuration.txt
+++ b/doc/configuration.txt
@@ -6595,7 +6595,7 @@
 
     frontend fe
       bind 10.42.0.1:80
-      http-request do-resolve(txn.myip,mydns,ipv4) hdr(Host),lower,regsub(:[0-9]*$,)
+      http-request do-resolve(txn.myip,mydns,ipv4) hdr(Host),host_only
       http-request capture var(txn.myip) len 40
 
       # return 503 when the variable is not set,