Bump mockito-core from 2.12.0 to 3.3.3

Bumps [mockito-core](https://github.com/mockito/mockito) from 2.12.0 to 3.3.3.
- [Release notes](https://github.com/mockito/mockito/releases)
- [Commits](mockito/mockito@v2.12.0...v3.3.3)

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

Author: dependabot-preview[bot]

build.gradle

@@ -34,7 +34,7 @@ dependencies {
     compile "com.squareup.okhttp3:okhttp:${okhttp_version}"
 
     testCompile 'junit:junit:4.13'
-    testCompile 'org.mockito:mockito-core:2.12.0'
+    testCompile 'org.mockito:mockito-core:3.3.3'
     testCompile "com.squareup.okhttp3:mockwebserver:${okhttp_version}"
     testCompile 'org.assertj:assertj-core:3.10.0'
 }