Revert "Properly decode headers"

This reverts commit fa316fd0b3.

app/src/main/java/eu/faircode/email/MessageHelper.java

@@ -475,7 +475,6 @@ public class MessageHelper {
             return null;
 
         header = new String(header.getBytes(StandardCharsets.ISO_8859_1));
-        header = decodeMime(header);
         return InternetAddress.parseHeader(header, false);
     }