env_librados.h: drop redundant #endif (#4354)

Summary:
without this change, rocksdb_env_librados_test fails to build.

it's a regression introduced by 64324e32

Signed-off-by: Kefu Chai <tchaikov@gmail.com>
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4354

Differential Revision: D9702665

Pulled By: riversand963

fbshipit-source-id: 65134eaff0543733210edfc77f89c96709da7a3f

include/rocksdb/utilities/env_librados.h

@@ -173,4 +173,3 @@ class EnvLibrados : public EnvWrapper {
   friend class LibradosWritableFile;
 };
 }
-#endif