[chore] Remove redundant wait group from a test (open-telemetry#10269)

https://github.com/open-telemetry/opentelemetry-collector/pull/10258/files#r1621017272
made me wonder if the wait group is really necessary. We have another
synchronization that waits for at least two requests to enter the merge
function, which should be enough. So, we don't necessarily need this
wait group.

Co-authored-by: Alex Boten <223565+codeboten@users.noreply.github.com>

exporter/exporterhelper/batch_sender_test.go

@@ -443,9 +443,10 @@ func TestBatchSender_ShutdownDeadlock(t *testing.T) {
 	waitMerge := make(chan struct{}, 10)
 
 	// blockedBatchMergeFunc blocks until the blockMerge channel is closed
-	blockedBatchMergeFunc := func(_ context.Context, r1 Request, _ Request) (Request, error) {
+	blockedBatchMergeFunc := func(_ context.Context, r1 Request, r2 Request) (Request, error) {
 		waitMerge <- struct{}{}
 		<-blockMerge
+		r1.(*fakeRequest).items += r2.(*fakeRequest).items
 		return r1, nil
 	}
 
@@ -458,18 +459,11 @@ func TestBatchSender_ShutdownDeadlock(t *testing.T) {
 
 	sink := newFakeRequestSink()
 
-	// Send 10 concurrent requests and wait for them to start
-	startWG := sync.WaitGroup{}
-	for i := 0; i < 10; i++ {
-		startWG.Add(1)
-		go func() {
-			startWG.Done()
-			require.NoError(t, be.send(context.Background(), &fakeRequest{items: 4, sink: sink}))
-		}()
-	}
-	startWG.Wait()
+	// Send 2 concurrent requests
+	go func() { require.NoError(t, be.send(context.Background(), &fakeRequest{items: 4, sink: sink})) }()
+	go func() { require.NoError(t, be.send(context.Background(), &fakeRequest{items: 4, sink: sink})) }()
 
-	// Wait for at least one batch to enter the merge function
+	// Wait for the requests to enter the merge function
 	<-waitMerge
 
 	// Initiate the exporter shutdown, unblock the batch merge function to catch possible deadlocks,
@@ -485,12 +479,8 @@ func TestBatchSender_ShutdownDeadlock(t *testing.T) {
 	close(blockMerge)
 	<-doneShutdown
 
-	// The exporter should have sent only one "merged" batch, in some cases it might send two if the shutdown
-	// happens before the batch is fully merged.
-	assert.LessOrEqual(t, uint64(1), sink.requestsCount.Load())
-
-	// blockedBatchMergeFunc just returns the first request, so the items count should be 4 times the requests count.
-	assert.Equal(t, sink.requestsCount.Load()*4, sink.itemsCount.Load())
+	assert.EqualValues(t, 1, sink.requestsCount.Load())
+	assert.EqualValues(t, 8, sink.itemsCount.Load())
 }
 
 func queueBatchExporter(t *testing.T, batchOption Option) *baseExporter {