[SampleFDO] Fix MSVC "namespace uses itself" warning (NFC)
MSVC warning:
```
SampleProfileLoaderBaseImpl.h(41): warning C4515: 'llvm': namespace uses itself
```
GitOrigin-RevId: a23e6b321ca623b83252f8b1e06a2ad4fc441f89
diff --git a/include/llvm/Transforms/Utils/SampleProfileLoaderBaseImpl.h b/include/llvm/Transforms/Utils/SampleProfileLoaderBaseImpl.h
index eab9869..5abec6e 100644
--- a/include/llvm/Transforms/Utils/SampleProfileLoaderBaseImpl.h
+++ b/include/llvm/Transforms/Utils/SampleProfileLoaderBaseImpl.h
@@ -38,7 +38,6 @@
#include "llvm/Transforms/Utils/SampleProfileLoaderBaseUtil.h"
namespace llvm {
-using namespace llvm;
using namespace sampleprof;
using namespace sampleprofutil;
using ProfileCount = Function::ProfileCount;