prevent duplicate classes due to dependency rename

Signed-off-by: Andy Scherzinger <info@andy-scherzinger.de>

app/build.gradle

@@ -248,7 +248,9 @@ dependencies {
     implementation 'org.apache.commons:commons-lang3:3.12.0'
     implementation 'com.github.wooplr:Spotlight:1.3'
     implementation 'com.google.code.findbugs:jsr305:3.0.2'
-    implementation 'com.github.nextcloud-deps:ChatKit:0.4.0'
+    implementation ('com.github.nextcloud-deps:ChatKit:0.4.0', {
+        exclude group: 'com.google.android', module: 'flexbox'	// replaced by v3 not yet used here
+    })
 
     implementation 'joda-time:joda-time:2.12.4'
     implementation "io.coil-kt:coil:${coilKtVersion}"