Bump Robolectric to 4.6.1

The bug fix seems potentially serious and worth having:
https://github.com/robolectric/robolectric/releases/tag/robolectric-4.6.1

PiperOrigin-RevId: 383096745

constants.gradle

@@ -24,7 +24,7 @@ project.ext {
     guavaVersion = '27.1-android'
     guavaVersion = '27.1-android'
     mockitoVersion = '3.4.0'
     mockitoVersion = '3.4.0'
     mockWebServerVersion = '3.12.0'
     mockWebServerVersion = '3.12.0'
-    robolectricVersion = '4.6'
+    robolectricVersion = '4.6.1'
     checkerframeworkVersion = '3.3.0'
     checkerframeworkVersion = '3.3.0'
     checkerframeworkCompatVersion = '2.5.0'
     checkerframeworkCompatVersion = '2.5.0'
     jsr305Version = '3.0.2'
     jsr305Version = '3.0.2'