downgrade maven-release-plugin to 2.4.2, maven-scm-provider-gitexe to…

… 1.9.1, maven-site-plugin, maven-surefire-plugin

pom.xml

@@ -102,17 +102,17 @@ License.
     <maven-enforcer-plugin.version>3.1.0</maven-enforcer-plugin.version>
     <maven-javadoc-plugin.version>3.4.1</maven-javadoc-plugin.version>
     <maven-project-info-reports-plugin.version>3.4.1</maven-project-info-reports-plugin.version>
-    <maven-release-plugin.version>3.0.0-M6</maven-release-plugin.version>
-    <maven-scm-provider-gitexe.version>2.0.0-M2</maven-scm-provider-gitexe.version>
-    <maven-site-plugin.version>4.0.0-M3</maven-site-plugin.version>
+    <maven-release-plugin.version>2.4.2</maven-release-plugin.version>
+    <maven-scm-provider-gitexe.version>1.9.1</maven-scm-provider-gitexe.version>
+    <maven-site-plugin.version>3.12.1</maven-site-plugin.version>
     <maven-source-plugin.version>3.2.1</maven-source-plugin.version>
-    <maven-surefire-plugin.version>3.0.0-M7</maven-surefire-plugin.version>
+    <maven-surefire-plugin.version>2.22.2</maven-surefire-plugin.version>
     <scott-data-hsqldb.version>0.2</scott-data-hsqldb.version>
     <slf4j.version>2.0.3</slf4j.version>
 
     <maven-javadoc-plugin.additionalOptions>-html5</maven-javadoc-plugin.additionalOptions>
     <maven-javadoc-plugin.excludePackageNames>net.hydromatic.morel.parse</maven-javadoc-plugin.excludePackageNames>
-    <maven-javadoc-plugin.link>https://docs.oracle.com/javase/9/docs/api/</maven-javadoc-plugin.link>
+    <maven-javadoc-plugin.link>https://docs.oracle.com/javase/11/docs/api/</maven-javadoc-plugin.link>
   </properties>
 
   <!-- Environment settings. -->