Fix shrinker issue

app/src/main/java/org/tasks/preferences/AttributionActivity.java

@@ -2,6 +2,7 @@ package org.tasks.preferences;
 
 import android.content.Context;
 import android.os.Bundle;
+import androidx.annotation.Keep;
 import androidx.appcompat.app.AppCompatActivity;
 import androidx.appcompat.widget.Toolbar;
 import androidx.lifecycle.MutableLiveData;
@@ -93,6 +94,7 @@ public class AttributionActivity extends ThemedInjectingAppCompatActivity {
       return copyrightHolder;
     }
 
+    @Keep
     String getLicense() {
       return license;
     }