Remove test setup for no longer supported Gradle version

Author: jjohannes

src/test/groovy/org/gradlex/javamodule/moduleinfo/test/AbstractFunctionalTest.groovy

@@ -535,10 +535,6 @@ abstract class AbstractFunctionalTest extends Specification {
                 
                 ${libs.jarNameOnly? 'javaModulesMergeJars("org.apache.zookeeper:zookeeper")' : '' }
                 ${libs.jarNameOnly? 'javaModulesMergeJars("org.slf4j:slf4j-ext")' : '' }
-
-                // Before Gradle 6.8, there is no consistent resolution and versions need to be defined 
-                ${gradleVersionUnderTest == "6.4.1"? 'javaModulesMergeJars("org.apache.zookeeper:zookeeper:3.8.0")' : '' }
-                ${gradleVersionUnderTest == "6.4.1"? 'javaModulesMergeJars("org.slf4j:slf4j-ext:1.7.32")' : '' }
             }
             
             extraJavaModuleInfo {

src/test/groovy/org/gradlex/javamodule/moduleinfo/test/EdgeCasesFunctionalTest.groovy

@@ -67,7 +67,6 @@ class EdgeCasesFunctionalTest extends Specification {
     def "does fully merge zip files on the classpath"() {
         given:
         buildFile << """             
-            ${gradleVersionUnderTest == "6.4.1"? 'configurations.javaModulesMergeJars.get().extendsFrom(configurations.implementation.get())' : '' }
             dependencies {
                 implementation("org.apache.qpid:qpid-broker-core:9.0.0")
                 implementation("org.apache.qpid:qpid-broker-plugins-management-http:9.0.0")