Merge pull request #3279 from nextcloud/dependabot/gradle/org.mockito-mockito-core-2.23.4

Bump mockito-core from 2.23.0 to 2.23.4

build.gradle

@@ -245,7 +245,7 @@ dependencies {
 
     // dependencies for local unit tests
     testImplementation 'junit:junit:4.12'
-    testImplementation 'org.mockito:mockito-core:2.23.0'
+    testImplementation 'org.mockito:mockito-core:2.23.4'
     // dependencies for instrumented tests
     // JUnit4 Rules
     androidTestImplementation 'com.android.support.test:rules:1.0.2'