Update build plugins for spec doc project

Signed-off-by: Lukas Jungmann <lukas.jungmann@oracle.com>

spec/pom.xml

@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <!--
 
-    Copyright (c) 2018, 2020 Oracle and/or its affiliates. All rights reserved.
+    Copyright (c) 2018, 2022 Oracle and/or its affiliates. All rights reserved.
 
     This program and the accompanying materials are made available under the
     terms of the Eclipse Public License v. 2.0 which is available at
@@ -17,21 +17,21 @@
     <parent>
         <groupId>org.eclipse.ee4j</groupId>
         <artifactId>project</artifactId>
-        <version>1.0.6</version>
+        <version>1.0.7</version>
         <relativePath/>
     </parent>
     <modelVersion>4.0.0</modelVersion>
     <groupId>jakarta.persistence</groupId>
     <artifactId>persistence-spec</artifactId>
     <packaging>pom</packaging>
-    <version>3.1-SNAPSHOT</version>
+    <version>3.1</version>
     <name>Jakarta Persistence Specification</name>
 
     <properties>
         <site.output.dir>${project.build.directory}/staging</site.output.dir>
         <maven.site.skip>true</maven.site.skip>
-        <asciidoctor.maven.plugin.version>2.0.0</asciidoctor.maven.plugin.version>
-        <asciidoctorj.pdf.version>1.5.3</asciidoctorj.pdf.version>
+        <asciidoctor.maven.plugin.version>2.2.2</asciidoctor.maven.plugin.version>
+        <asciidoctorj.pdf.version>1.6.2</asciidoctorj.pdf.version>
         <spec.name>jakarta-${project.artifactId}-${project.version}</spec.name>
         <!-- status: DRAFT, BETA, etc., or blank for final -->
         <status>DRAFT</status>
@@ -58,7 +58,7 @@
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-enforcer-plugin</artifactId>
-                <version>3.0.0-M3</version>
+                <version>3.0.0</version>
                 <executions>
                     <execution>
                         <id>enforce-versions</id>
@@ -68,8 +68,8 @@
                         <configuration>
                             <rules>
                                 <requireJavaVersion>
-                                    <version>[1.8,)</version>
-                                    <message>You need JDK8 or newer</message>
+                                    <version>[11,)</version>
+                                    <message>You need Java SE 11 or newer</message>
                                 </requireJavaVersion>
                             </rules>
                         </configuration>
@@ -157,7 +157,7 @@
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-assembly-plugin</artifactId>
-                <version>3.2.0</version>
+                <version>3.3.0</version>
                 <inherited>false</inherited>
                 <executions>
                     <execution>