NCBC-4190: Bucket manager had redundant code

Motivation
==========
Recent commit left an extra check for success in a call.  Simple
fix.

Modification
============
Just removed the few lines.

Result
======
Tests pass fine.

Change-Id: Ic767d50d51c6543e1abbb6be5b954f11ffae23d6
Reviewed-on: https://review.couchbase.org/c/couchbase-net-client/+/242537
Reviewed-by: Emilien Bevierre <emilien.bevierre@couchbase.com>
Tested-by: Build Bot <build@couchbase.com>

Author: davidkelly

src/Couchbase/Management/Buckets/BucketManager.cs

@@ -363,12 +363,6 @@ public async Task FlushBucketAsync(string bucketName, FlushBucketOptions? option
                     Statement = uri.ToString()
                 };
 
-                if (result.IsSuccessStatusCode)
-                {
-                    rootSpan.SetStatus(RequestSpanStatusCode.Ok);
-                    return;
-                }
-
                 switch (result.StatusCode)
                 {
                     case HttpStatusCode.NotFound: