Bump mockito-core from 3.12.3 to 3.12.4 (#123)

Bumps [mockito-core](https://github.com/mockito/mockito) from 3.12.3 to 3.12.4.
- [Release notes](https://github.com/mockito/mockito/releases)
- [Commits](mockito/mockito@v3.12.3...v3.12.4)

---
updated-dependencies:
- dependency-name: org.mockito:mockito-core
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

build.gradle

@@ -51,7 +51,7 @@ dependencies {
     compile "io.reactivex.rxjava3:rxjava:3.1.0"
 
     testCompile group: 'junit', name: 'junit', version: '4.13.2'
-    testCompile 'org.mockito:mockito-core:3.12.3'
+    testCompile 'org.mockito:mockito-core:3.12.4'
 }
 
 apply plugin: 'maven'