Remove illegal dependsOn edges in MPP tests

Those dependsOn edges were not used in any way, and not assertion
checked for them. They are illegal according to KPM design, and
we generally consider such a setup unsupported with the stable MPP
plugin, too.

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/new-mpp-lib-and-app/sample-external-lib/build.gradle

@@ -79,7 +79,6 @@ apply plugin: 'maven-publish'
 afterEvaluate {
     kotlin {
         jvm('jvm6').compilations.create('benchmark') {
-            defaultSourceSet.dependsOn(sourceSets.jvm6Main)
             assemble.dependsOn compileKotlinTask
         }
     }

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/new-mpp-lib-and-app/sample-lib-gradle-kotlin-dsl/build.gradle.kts

@@ -55,7 +55,6 @@ publishing {
 afterEvaluate {
     kotlin {
         jvm("jvm6").compilations.create("benchmark") {
-            defaultSourceSet.dependsOn(sourceSets["jvm6Main"])
             tasks["assemble"].dependsOn(compileKotlinTask)
         }
     }

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/new-mpp-lib-and-app/sample-lib/build.gradle

@@ -103,7 +103,6 @@ publishing {
 afterEvaluate {
     kotlin {
         jvm('jvm6').compilations.create('benchmark') {
-            defaultSourceSet.dependsOn(sourceSets.jvm6Main)
             assemble.dependsOn compileKotlinTask
         }
     }