Revert "Added an empty __init__.py file to the MLIR Python bindings"

This reverts commit b50893db52.

Post-commit review pointed out that adding this file will require the
entire Python tree (including out-of-tree projects) to come from the
same directory, which might be problematic in non-default installations.
Reverting pending further discussion.

mlir/python/mlir/__init__.py

@@ -1,3 +0,0 @@
-# Licensed under the Apache License v2.0 with LLVM Exceptions.
-# See https://llvm.org/LICENSE.txt for license information.
-# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception