Bump robolectric from 4.6.1 to 4.7.3

Bumps [robolectric](https://github.com/robolectric/robolectric) from 4.6.1 to 4.7.3.
- [Release notes](https://github.com/robolectric/robolectric/releases)
- [Commits](https://github.com/robolectric/robolectric/compare/robolectric-4.6.1...robolectric-4.7.3)

---
updated-dependencies:
- dependency-name: org.robolectric:robolectric
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

dependencies.gradle

@@ -37,7 +37,7 @@ ext.versions = [
         mockitoKotlin        : "4.0.0",
         kluent               : "1.68",
         apacheCodecs         : "1.15",
-        robolectric          : "4.6.1",
+        robolectric          : "4.7.3",
         dexter               : "6.2.3",
         timber               : "4.7.1",
         fastScroll           : "2.0.1",