Replace proprietary headers with Apache 2.0 copyright headers in PrivacyGuard shadow_model_training

[mgrange1998]

Summary:
Adds Apache License 2.0 copyright headers to seven source and test files under privacy_guard/shadow_model_training, replacing the internal confidential header. This aligns the repo with OSS compliance and satisfies the COPYRIGHT_HEADERS_EXIST check from the Open Source Automated Checkup.

These files were recently added w/ the shadow model training module.

COPYRIGHT_HEADERS_EXIST: Copyright Headers
****************************************
FIX IT! https://our.intern.facebook.com/intern/opensource/github/repo/2059348974551169/repo_settings/header_exemptions/
Every project specific source file must contain a doc block with an appropriate copyright header. Unrelated files must be listed as exceptions in the Copyright Headers Exceptions page in the repo dashboard.
A copyright header clearly indicates that the code is owned by Meta. Every open source file must start with a comment containing "Meta Platforms, Inc. and affiliates"
https://github.com/facebookresearch/PrivacyGuard/blob/main/privacy_guard/shadow_model_training/dataset.py:
The first 16 lines of 'privacy_guard/shadow_model_training/dataset.py' do not contain the patterns:
	Copyright
https://github.com/facebookresearch/PrivacyGuard/blob/main/privacy_guard/shadow_model_training/model.py:
The first 16 lines of 'privacy_guard/shadow_model_training/model.py' do not contain the patterns:
	Copyright
https://github.com/facebookresearch/PrivacyGuard/blob/main/privacy_guard/shadow_model_training/training.py:
The first 16 lines of 'privacy_guard/shadow_model_training/training.py' do not contain the patterns:
	Copyright
https://github.com/facebookresearch/PrivacyGuard/blob/main/privacy_guard/shadow_model_training/visualization.py:
The first 16 lines of 'privacy_guard/shadow_model_training/visualization.py' do not contain the patterns:
	Copyright
https://github.com/facebookresearch/PrivacyGuard/blob/main/privacy_guard/shadow_model_training/tests/test_dataset.py:
The first 16 lines of 'privacy_guard/shadow_model_training/tests/test_dataset.py' do not contain the patterns:
	Copyright
https://github.com/facebookresearch/PrivacyGuard/blob/main/privacy_guard/shadow_model_training/tests/test_model.py:
The first 16 lines of 'privacy_guard/shadow_model_training/tests/test_model.py' do not contain the patterns:
	Copyright
https://github.com/facebookresearch/PrivacyGuard/blob/main/privacy_guard/shadow_model_training/tests/test_training.py:
The first 16 lines of 'privacy_guard/shadow_model_training/tests/test_training.py' do not contain the patterns:
	Copyright

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Session: DEV42745488

Differential Revision: D91036757

[meta-codesync]

@mgrange1998 has exported this pull request. If you are a Meta employee, you can view the originating Diff in D91036757.

[meta-codesync]

This pull request has been merged in 59c8b05.