Revert "Added transaction to fix threads"

This reverts commit cf2fa0d907.

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

@@ -875,9 +875,6 @@ public class MessageHelper {
 
         String thread = null;
         DB db = DB.getInstance(context);
-        try {
-            db.beginTransaction();
-
         for (String ref : refs) {
             List<EntityMessage> messages = db.message().getMessagesByMsgId(account, ref);
             for (EntityMessage message : messages) {
@@ -887,12 +884,6 @@ public class MessageHelper {
                     db.message().setMessageThread(message.id, thread);
             }
         }
-
-            db.setTransactionSuccessful();
-        } finally {
-            db.endTransaction();
-        }
-
         if (thread != null)
             return thread;