linked: fix colors for dark theme

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

@@ -156,7 +156,7 @@
                     android:drawableLeft="@drawable/ic_repeat_black_24dp"
                     android:drawableStart="@drawable/ic_repeat_black_24dp"
                     android:drawablePadding="12dp"
-                    android:text="@string/linked_button_retry"
+                    android:text="@string/linked_button_retry_step"
                     android:id="@+id/button_retry"
                     />
 

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

@@ -6,7 +6,6 @@
     android:minHeight="?android:attr/listPreferredItemHeight"
     android:orientation="horizontal"
     android:singleLine="true"
-    android:background="#ffffff"
     tools:showIn="@layout/linked_id_view_fragment">
 
     <ImageView

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

@@ -14,7 +14,7 @@
         android:transitionName="card_linked_ids"
         android:layout_width="match_parent"
         android:layout_height="wrap_content"
-        card_view:cardBackgroundColor="@android:color/white"
+        card_view:cardBackgroundColor="?attr/colorCardViewBackground"
         card_view:cardElevation="2dp"
         card_view:cardUseCompatPadding="true"
         card_view:cardCornerRadius="4dp">

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

@@ -17,7 +17,7 @@
         android:layout_height="wrap_content"
         android:visibility="gone"
         tools:visibility="visible"
-        card_view:cardBackgroundColor="@android:color/white"
+        card_view:cardBackgroundColor="?attr/colorCardViewBackground"
         card_view:cardElevation="2dp"
         card_view:cardUseCompatPadding="true"
         card_view:cardCornerRadius="4dp">