pw_transfer: Remove duplicated test line

This line was accidentally copied & pasted.

Change-Id: I67f4e82fdc90f1ef23af85e2f81e2428a36bf3ee
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/122952
Commit-Queue: Auto-Submit <auto-submit@pigweed.google.com.iam.gserviceaccount.com>
Reviewed-by: Rob Mohr <mohrr@google.com>
Pigweed-Auto-Submit: Alexei Frolov <frolv@google.com>
diff --git a/pw_transfer/transfer_thread_test.cc b/pw_transfer/transfer_thread_test.cc
index 8f06337..d83f829 100644
--- a/pw_transfer/transfer_thread_test.cc
+++ b/pw_transfer/transfer_thread_test.cc
@@ -224,7 +224,6 @@
       3,
       10);
   transfer_thread_.WaitUntilEventIsProcessed();
-  transfer_thread_.WaitUntilEventIsProcessed();
 
   // First transfer starts correctly.
   EXPECT_TRUE(handler3.prepare_read_called);