Ignore test: PreviewImageActivityIT

My local test run worked, but it took 10 minutes per test case. Reason
seems to be a very long wait after the next screen is displayed.

Signed-off-by: Philipp Hasper <vcs@hasper.info>

Author: PhilLab

app/src/androidTest/java/com/owncloud/android/ui/preview/PreviewImageActivityIT.kt

@@ -39,6 +39,7 @@ import org.junit.Ignore
 import org.junit.Test
 import java.io.File
 
+@Ignore("Investigating Drone CI timeout")
 class PreviewImageActivityIT : AbstractOnServerIT() {
     companion object {
         private const val REMOTE_FOLDER: String = "/PreviewImageActivityIT/"