Fix documentation of pgrowlocks using "lock_type" instead of "modes"

The example used in the documentation is outdated as well.  This is an
oversight from 0ac5ad51, which bumped up pgrowlocks but forgot some bits
of the documentation.

Reported-by: Chris Wilson
Discussion: https://postgr.es/m/153838692816.2950.12001142346234155699@wrigleys.postgresql.org
Backpatch-through: 9.3

doc/src/sgml/pgrowlocks.sgml

@@ -70,7 +70,7 @@ pgrowlocks(text) returns setof record
       <entry>Transaction IDs of lockers (more than one if multitransaction)</entry>
      </row>
      <row>
-      <entry><structfield>lock_type</structfield></entry>
+      <entry><structfield>modes</structfield></entry>
       <entry><type>text[]</type></entry>
       <entry>Lock mode of lockers (more than one if multitransaction),
        an array of <literal>Key Share</literal>, <literal>Share</literal>,
@@ -127,14 +127,14 @@ SELECT * FROM accounts AS a, pgrowlocks('accounts') AS p
  <sect2>
   <title>Sample Output</title>
 
-<screen>
-test=# SELECT * FROM pgrowlocks('t1');
- locked_row | lock_type | locker | multi |   xids    |     pids
-------------+-----------+--------+-------+-----------+---------------
-      (0,1) | Shared    |     19 | t     | {804,805} | {29066,29068}
-      (0,2) | Shared    |     19 | t     | {804,805} | {29066,29068}
-      (0,3) | Exclusive |    804 | f     | {804}     | {29066}
-      (0,4) | Exclusive |    804 | f     | {804}     | {29066}
+  <screen>
+=# SELECT * FROM pgrowlocks('t1');
+ locked_row | locker | multi | xids  |     modes      |  pids
+------------+--------+-------+-------+----------------+--------
+ (0,1)      |    609 | f     | {609} | {"For Share"}  | {3161}
+ (0,2)      |    609 | f     | {609} | {"For Share"}  | {3161}
+ (0,3)      |    607 | f     | {607} | {"For Update"} | {3107}
+ (0,4)      |    607 | f     | {607} | {"For Update"} | {3107}
 (4 rows)
 </screen>
  </sect2>