docs: Fix column count attribute in table

Nothing seems to actually depend on the attribute, as the docs built
successfully, but let's be tidy.

Reported offlist by Matthias van de Meent

diff --git a/doc/src/sgml/protocol.sgml b/doc/src/sgml/protocol.sgml
index d73e4d6dbdf0086bc41b1267fd57b33dfe22ffad..a746c967053d2e1734d777177e7d90d2de37aad1 100644 (file)
--- a/doc/src/sgml/protocol.sgml
+++ b/doc/src/sgml/protocol.sgml
@@ -223,7 +223,7 @@
    <table>
     <title>Protocol versions</title>
 
-    <tgroup cols="2">
+    <tgroup cols="3">
      <thead>
       <row>
        <entry>Version</entry>