Merge pull request #8250 from nextcloud/dependabot/gradle/mockitoVersion-3.9.0

Bump mockitoVersion from 3.8.0 to 3.9.0

build.gradle

@@ -60,7 +60,7 @@ ext {
     prismVersion = "2.0.0"
     butterknifeVersion = "10.2.3"
     androidLibraryVersion = "master-SNAPSHOT"
-    mockitoVersion = "3.8.0"
+    mockitoVersion = "3.9.0"
     mockkVersion = "1.10.4"
     powermockVersion = "2.0.9"
     byteBuddyVersion = "1.10.22"