Correct ALTER TYPE -> SET DATA TYPE in ALTER TABLE documentation.

The latter is the correct name of the operation to change the data type
of a column.

Noah Misch

doc/src/sgml/ref/alter_table.sgml

@@ -777,7 +777,7 @@ ALTER TABLE <replaceable class="PARAMETER">name</replaceable>
    </para>
 
    <para>
-    The fact that <literal>ALTER TYPE</> requires rewriting the whole table
+    The fact that <literal>SET DATA TYPE</> requires rewriting the whole table
     is sometimes an advantage, because the rewriting process eliminates
     any dead space in the table.  For example, to reclaim the space occupied
     by a dropped column immediately, the fastest way is:
@@ -792,15 +792,15 @@ ALTER TABLE table ALTER COLUMN anycol TYPE anytype;
    </para>
 
    <para>
-    The <literal>USING</literal> option of <literal>ALTER TYPE</> can actually
+    The <literal>USING</literal> option of <literal>SET DATA TYPE</> can actually
     specify any expression involving the old values of the row; that is, it
     can refer to other columns as well as the one being converted.  This allows
-    very general conversions to be done with the <literal>ALTER TYPE</>
+    very general conversions to be done with the <literal>SET DATA TYPE</>
     syntax.  Because of this flexibility, the <literal>USING</literal>
     expression is not applied to the column's default value (if any); the
     result might not be a constant expression as required for a default.
     This means that when there is no implicit or assignment cast from old to
-    new type, <literal>ALTER TYPE</> might fail to convert the default even
+    new type, <literal>SET DATA TYPE</> might fail to convert the default even
     though a <literal>USING</literal> clause is supplied.  In such cases,
     drop the default with <literal>DROP DEFAULT</>, perform the <literal>ALTER
     TYPE</>, and then use <literal>SET DEFAULT</> to add a suitable new