Update xfunc.sgml

Author: ChenHuajun

postgresql/doc/src/sgml/xfunc.sgml

@@ -1605,7 +1605,7 @@ SELECT mleast(10, -1, 5, 4.4);
      array, as if you had written
 
 <screen>
-SELECT mleast(ARRAY[10, -1, 5, 4.4]);    -- doesn't work
+SELECT mleast(ARRAY[10, -1, 5, 4.4]);    -&minus; doesn't work
 </screen>
 
      You can't actually write that, though &mdash; or at least, it will
@@ -1852,7 +1852,7 @@ SELECT foo(10);
   15
 (1 row)
 
-SELECT foo();  -&minus; 因为第一个参数没有默认值，所以失败
+SELECT foo();  -- 因为第一个参数没有默认值，所以失败
 ERROR:  function foo() does not exist
 </screen>
      <literal>=</literal>符号也可以用来代替关键字<literal>DEFAULT</literal>。