Remove unused and duplicate includes from SingleWriterFixedHashMapTest.cpp

Summary:
Removed two unnecessary `#include` directives from `SingleWriterFixedHashMapTest.cpp`:

- `#include <glog/logging.h>`: No `LOG()`, `CHECK()`, `DCHECK()`, or any other glog macro is used in this file.
- `#include <folly/synchronization/test/Barrier.h>`: Duplicate of an identical include already present earlier in the file (line 23).
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Reviewed By: lexprfuncall

Differential Revision: D95403721

fbshipit-source-id: cefe1df1ae5b990eae114fa9b08d9d51b3eef83e

Author: yfeldblum

third-party/folly/src/folly/concurrency/container/test/SingleWriterFixedHashMapTest.cpp

@@ -22,9 +22,6 @@
 #include <folly/portability/GTest.h>
 #include <folly/synchronization/test/Barrier.h>
 
-#include <glog/logging.h>
-#include <folly/synchronization/test/Barrier.h>
-
 #include <atomic>
 #include <iomanip>
 #include <thread>