Changed to 301-redirect to apidocs/index.html

Previously, we had changed to serving the content directly to workaround
[MJAVADOC-539] Upgrading plugin from 3.0.0 to 3.0.1 and 3.1.0 breaks certain external javadoc links.

MJAVADOC-539 has been fixed.  Furthermore, our builds all use offline linking based on "javadoc"
classifier artifacts, so this bug is not relevant anyway.

We are making this change to avoid any possibly duplicate content issues between the two representations.

book/src/main/resources-filtered/META-INF/resources/persistence/apidocs/index.jspx

@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <!--
 ao-persistence - Highly efficient persistent collections for Java.
-Copyright (C) 2020, 2021, 2022  AO Industries, Inc.
+Copyright (C) 2020, 2021, 2022, 2023  AO Industries, Inc.
     support@aoindustries.com
     7262 Bull Pen Cir
     Mobile, AL 36695
@@ -32,8 +32,7 @@ along with ao-persistence.  If not, see <https://www.gnu.org/licenses/>.
   <jsp:directive.page session="false" />
   <jsp:output omit-xml-declaration="true" />
   <c:if test="${core:getCaptureLevel() == null and empty param.view and !param.navigation}">
-    <jsp:directive.page contentType="text/html" />
-    <ao:forward page="index.html" />
+    <ao:redirect page="index.html" statusCode="301" addLastModified="false" />
   </c:if>
   <core:page
     title="@{documented.name} ${ao:getProjectVersion('./', 'com.aoapps', 'ao-persistence', '¿@{project.version}?')} API Docs"