Enable linting: lint config changes plus arc lint command (#3966)

Summary:
Pull Request resolved: #3966

This actually enables the linting.

Manual changes:
- tools/arcanist/lint/fbsource-licenselint-config.toml
- tools/arcanist/lint/fbsource-lint-engine.toml

Automated changes:
`arc lint --apply-patches --take LICENSELINT --paths-cmd 'hg files faiss'`

Reviewed By: asadoughi

Differential Revision: D64484165

fbshipit-source-id: 4f2f6e953c94ef6ebfea8a5ae035ccfbea65ed04

Author: Michael Norris

benchs/CMakeLists.txt

@@ -1,7 +1,6 @@
-# Copyright (c) Facebook, Inc. and its affiliates.
-# All rights reserved.
+# Copyright (c) Meta Platforms, Inc. and affiliates.
 #
-# This source code is licensed under the BSD-style license found in the
+# This source code is licensed under the MIT license found in the
 # LICENSE file in the root directory of this source tree.
 
 

benchs/bench_6bit_codec.cpp

@@ -1,5 +1,5 @@
-/**
- * Copyright (c) Facebook, Inc. and its affiliates.
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
  *
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.