Fix attachment indicator for screen reader users

Some screen readers present attachment indicator twice, once as part of populated content description of a message item, second time as an image with content description. To improve the behaviour, remove the content description from the image so it won't be reported.

Signed-off-by: Peter Vágner <pvdeejay@gmail.com>

app/src/main/res/layout/include_message_compact.xml

@@ -240,7 +240,6 @@
         android:layout_width="21dp"
         android:layout_height="21dp"
         android:layout_marginStart="6dp"
-        android:contentDescription="@string/title_legend_attachment"
         app:layout_constraintBottom_toBottomOf="@+id/tvSubject"
         app:layout_constraintStart_toEndOf="@id/ivForwarded"
         app:layout_constraintTop_toTopOf="@+id/tvSubject"

app/src/main/res/layout/include_message_normal.xml

@@ -279,7 +279,6 @@
         android:layout_width="21dp"
         android:layout_height="21dp"
         android:layout_marginStart="6dp"
-        android:contentDescription="@string/title_legend_attachment"
         app:layout_constraintBottom_toBottomOf="@+id/tvFolder"
         app:layout_constraintStart_toEndOf="@id/ivForwarded"
         app:layout_constraintTop_toTopOf="@+id/tvFolder"