build.gradle: Don't specify output.resourcesDir for apiUsageSample

The apiUsageSample source set does not contain any resources, so there
is no need to specify an output dir for resources.

Furthermore, specifying the same output dir for classes and resources
causes Gradle to put the .class files in tests/d8_api_usage_sample.jar
and tests/r8_api_usage_sample.jar twice. This is ignored by the JVM,
but other tools (e.g. R8) might not handle duplicate classes in JARs.

Change-Id: If37aa127dc288992facfbad28a658ed4fa3ea538
diff --git a/build.gradle b/build.gradle
index 8ee6b41..cd831cc 100644
--- a/build.gradle
+++ b/build.gradle
@@ -113,7 +113,6 @@
         java {
             srcDirs = ['src/test/apiUsageSample']
         }
-        output.resourcesDir = 'build/classes/apiUsageSample'
     }
     debugTestResources {
         java {