Update Robolectric SDK to 31

Update Robolectric SDK to 31

Bug: 206905117
Test: Manual
Change-Id: I918e3d29ecc7d853802a34bae0728fd737b9539b
diff --git a/robolectric_tests/Android.mk b/robolectric_tests/Android.mk
index 1117cc3..7d9b0e1 100644
--- a/robolectric_tests/Android.mk
+++ b/robolectric_tests/Android.mk
@@ -29,7 +29,7 @@
     mockito-robolectric-prebuilt \
     truth-prebuilt
 LOCAL_JAVA_LIBRARIES := \
-    platform-robolectric-3.6.2-prebuilt
+    platform-robolectric-4.5.1-prebuilt
 
 LOCAL_JAVA_RESOURCE_DIRS := config