Switch from junit_binary to robolectric_binary.

This was done in:
https://chromium-review.googlesource.com/c/chromium/src/+/3709093
https://chromium-review.googlesource.com/c/chromium/src/+/3732850

Bug: chromium:1336818, b/237612564
Change-Id: Ie1394ffa16a7c3322aa774e94aee93e6b1ac6ed6
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/267167
Reviewed-by: Andrey Logvin <landrey@webrtc.org>
Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
Auto-Submit: Mirko Bonadei <mbonadei@webrtc.org>
Commit-Queue: Andrey Logvin <landrey@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#37376}
diff --git a/examples/BUILD.gn b/examples/BUILD.gn
index 031d5ac..26a51b2 100644
--- a/examples/BUILD.gn
+++ b/examples/BUILD.gn
@@ -904,7 +904,7 @@
     ]
   }
 
-  junit_binary("android_examples_junit_tests") {
+  robolectric_binary("android_examples_junit_tests") {
     sources = [
       "androidjunit/src/org/appspot/apprtc/BluetoothManagerTest.java",
       "androidjunit/src/org/appspot/apprtc/DirectRTCClientTest.java",