Replace *[]string with []string in product variables

There is no need for *[]string, []string can already hold a nil
value to specify "not set".

Test: all soong tests
Change-Id: I85a51b042c12aee1565a9287d62924feeeafd486
diff --git a/java/java_test.go b/java/java_test.go
index a0b8952..57b2a59 100644
--- a/java/java_test.go
+++ b/java/java_test.go
@@ -61,7 +61,7 @@
 		env["ANDROID_JAVA8_HOME"] = "jdk8"
 	}
 	config := android.TestArchConfig(buildDir, env)
-	config.TestProductVariables.DeviceSystemSdkVersions = &[]string{"14", "15"}
+	config.TestProductVariables.DeviceSystemSdkVersions = []string{"14", "15"}
 	return config
 
 }