Fix margins of dialog views

OpenKeychain/src/main/res/layout/view_key_delete_fragment.xml

@@ -1,6 +1,10 @@
 <?xml version="1.0" encoding="utf-8"?>
 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
     android:orientation="vertical"
+    android:paddingTop="16dp"
+    android:paddingBottom="16dp"
+    android:paddingLeft="24dp"
+    android:paddingRight="24dp"
     android:layout_width="match_parent"
     android:layout_height="match_parent">
 
@@ -8,7 +12,6 @@
         android:layout_width="match_parent"
         android:layout_height="wrap_content"
         android:id="@+id/mainMessage"
-        android:layout_margin="4dp"
         android:textAppearance="?android:textAppearanceMedium" />
 
 </LinearLayout>