doc: CREATE FOREIGN TABLE .. PARTITION OF .. DEFAULT

It looks like the docs weren't updated in 6f6b99d13 for v11.

The docs also seem to omit "FOR VALUES" literal.
And don't define partition_bound_spec (which I didn't fix here).

diff --git a/doc/src/sgml/ref/create_foreign_table.sgml b/doc/src/sgml/ref/create_foreign_table.sgml
index b374d8645db..1f1c4a52a2a 100644
--- a/doc/src/sgml/ref/create_foreign_table.sgml
+++ b/doc/src/sgml/ref/create_foreign_table.sgml
@@ -35,7 +35,8 @@ CREATE FOREIGN TABLE [ IF NOT EXISTS ] <replaceable class="parameter">table_name
   { <replaceable class="parameter">column_name</replaceable> [ WITH OPTIONS ] [ <replaceable
class="parameter">column_constraint</replaceable>[ ... ] ]
 
     | <replaceable>table_constraint</replaceable> }
     [, ... ]
-) ] <replaceable class="parameter">partition_bound_spec</replaceable>
+) ]
+  { FOR VALUES <replaceable class="parameter">partition_bound_spec</replaceable> | DEFAULT }
   SERVER <replaceable class="parameter">server_name</replaceable>
 [ OPTIONS ( <replaceable class="parameter">option</replaceable> '<replaceable class="parameter">value</replaceable>'
[,... ] ) ]