Fix dependencies on Gradle plugin marker artifacts in integration tests

Only `pom.xml` is published at `io.quarkus:io.quarkus.gradle.plugin` GA coordinates. Same for `io.quarkus.extension`.

See https://docs.gradle.org/current/userguide/plugins.html#sec:plugin_markers

Signed-off-by: Konstantin Gribov <grossws@gmail.com>

integration-tests/gradle/pom.xml

@@ -27,11 +27,13 @@
             <groupId>io.quarkus</groupId>
             <artifactId>io.quarkus.gradle.plugin</artifactId>
             <version>${project.version}</version>
+            <type>pom</type>
         </dependency>
         <dependency>
             <groupId>io.quarkus.extension</groupId>
             <artifactId>io.quarkus.extension.gradle.plugin</artifactId>
             <version>${project.version}</version>
+            <type>pom</type>
         </dependency>
         <dependency>
             <groupId>org.assertj</groupId>