updater_sample: Use stubs libs for android.test.base / runner.

To address the warning below (which will be disallowed):
bootable/recovery/updater_sample/tests/Android.mk: warning:
SystemUpdaterSampleTests (java:system) should not link to
android.test.runner (java:platform)

(See b/69899800 or the commit message in [1] for detailed discussions.)

[1]: https://android-review.googlesource.com/c/platform/frameworks/ml/+/666428

Test: `mmma -j bootable/recovery` gives no warning.
Test: Install and run SystemUpdaterSampleTests on device.
Change-Id: I12a1556d572d9f332fcf43dc84cbe8fd1b6df89b

updater_sample/tests/Android.mk

@@ -21,8 +21,8 @@ LOCAL_PACKAGE_NAME := SystemUpdaterSampleTests
 LOCAL_SDK_VERSION := system_current
 LOCAL_MODULE_TAGS := tests
 LOCAL_JAVA_LIBRARIES := \
-    android.test.runner \
-    android.test.base
+    android.test.base.stubs \
+    android.test.runner.stubs
 LOCAL_STATIC_JAVA_LIBRARIES := android-support-test
 LOCAL_INSTRUMENTATION_FOR := SystemUpdaterSample
 LOCAL_PROGUARD_ENABLED := disabled