[IMT] Remove duplicate unit test.
[IMT] Remove duplicate unit test.

The IMT tests were both registered with ROOT_ADD_GTEST and
ROOT_ADD_UNITTEST_DIR. The latter was removed.

karies/root,root-mirror/root,karies/root,olifre/root,root-mirror/root,olifre/root,karies/root,karies/root,olifre/root,root-mirror/root,root-mirror/root,karies/root,karies/root,olifre/root,olifre/root,root-mirror/root,karies/root,karies/root,root-mirror/root,olifre/root,root-mirror/root,root-mirror/root,olifre/root,olifre/root,root-mirror/root,olifre/root,olifre/root,root-mirror/root,karies/root,olifre/root,root-mirror/root,karies/root,karies/root