Remove "default subst" in profiler test, we don't need them.

hpvm/test/dnn_benchmarks/profiling/lit.cfg.py

@@ -28,7 +28,5 @@ config.test_exec_root = current_binary_dir
 # Tweak the PATH to include the tools dir.
 llvm_config.with_environment("PATH", config.llvm_tools_dir, append_path=True)
 
-llvm_config.use_default_substitutions()
-
 # Add substitution for our main script in this directory.
 llvm_config.add_tool_substitutions(["test_hpvm_c_profiling.py"], config.test_source_root)