Downgrade hsqldb for java 1.6

pom.xml

@@ -86,7 +86,7 @@
             <dependency>
                 <groupId>org.hsqldb</groupId>
                 <artifactId>hsqldb</artifactId>
-                <version>2.4.0</version>
+                <version>${hsql.version}</version>
                 <scope>test</scope>
                 <optional>true</optional>
             </dependency>
@@ -218,6 +218,7 @@
                 <maven.javadoc.skip>true</maven.javadoc.skip>
                 <jar.classifier>jdk16</jar.classifier>
                 <derby.version>10.12.1.1</derby.version>
+                <hsql.version>2.3.5</hsql.version>
                 <h2.version>1.4.191</h2.version>
                 <postgresql.version>42.2.2.jre6</postgresql.version>
                 <mariadb.version>1.7.3</mariadb.version>
@@ -326,6 +327,7 @@
             </activation>
             <properties>
                 <derby.version>10.14.2.0</derby.version>
+                <hsql.version>2.4.0</hsql.version>
                 <h2.version>1.4.197</h2.version>
                 <postgresql.version>42.2.2</postgresql.version>
                 <mariadb.version>2.2.4</mariadb.version>