chore: Update copyright headers

[lucasmcdonald3]

Issue #, if available:

Description of changes:

Update copyright headers from verbose copyright headers that get out of date to concise evergreen copyright headers.

Ctrl+Fs' that are now empty:

• # Copyright 20: 0 results.
• ^(?<![\s\S\r])(?!#).* (regex matching files that don't start with a #; i.e. audit for files that don't already have a copyright header)
  • 5 Python files still match this regex, but I won't add them:
  • 3 setup.py files (aws_encryption_sdk, test_vector_handlers, and decrypt_oracle)
  • decrypt_oracle/.chalice/build-requirements.py
  • decrypt_oracle/.chalice/pipeline.py

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

Check any applicable:

• [ ] Were any files moved? Moving files changes their URL, which breaks all hyperlinks to the files.