Fix pg_lo_import return type (#4785)

Author: VincentLanglet

reference/pgsql/functions/pg-lo-import.xml

@@ -10,7 +10,7 @@
  <refsect1 role="description">
   &reftitle.description;
   <methodsynopsis>
-   <type>int</type><methodname>pg_lo_import</methodname>
+   <type>int|string|false</type><methodname>pg_lo_import</methodname>
    <methodparam choice="opt"><type>PgSql\Connection</type><parameter>connection</parameter></methodparam>
    <methodparam><type>string</type><parameter>pathname</parameter></methodparam>
    <methodparam choice="opt"><type>mixed</type><parameter>object_id</parameter></methodparam>