docs - change gpbackup API version to current version 0.3.0 (#6471)

gpdb-doc/dita/admin_guide/managing/plugin_api/plugin_api_version.xml

@@ -11,10 +11,14 @@
     </section>
     <section id="section3">
       <title>Description</title>
-      <p><codeph>gpbackup</codeph> and <codeph>gprestore</codeph> invoke the <codeph>plugin_api_version</codeph> plugin command before a backup or restore operation to determine Backup Storage Plugin API version compatibility.</p>
+      <p><codeph>gpbackup</codeph> and <codeph>gprestore</codeph> invoke the
+          <codeph>plugin_api_version</codeph> plugin command before a backup or restore operation to
+        determine Backup Storage Plugin API version compatibility.</p>
     </section>
-    <section id="section5"><title>Return Value</title>
-      <p>The <codeph>plugin_api_version</codeph> command must return the Backup Storage Plugin API version number supported by the storage plugin, "0.1.0".</p>
+    <section id="section5">
+      <title>Return Value</title>
+      <p>The <codeph>plugin_api_version</codeph> command must return the Backup Storage Plugin API
+        version number supported by the storage plugin, "0.3.0".</p>
     </section>
   </body>
 </topic>