Standardize LICENSE body text formatting (#2992)

This cleans up a number of unnecessary differences in the LICENSE files:
- Removes C++ comments ("// ") from the beginnings of all the lines in license files that had them.
- Standardizes on having a blank line after the copyright line.
- Standardizes on having the final newline in the file.
- Standardizes on the indentation of the bulleted conditions.
- Standardizes on the locations of line breaks (re-wrapping the text)

This makes the license bodies--not including the copyright line--in almost all files the same, and matches the exact formatting already used in flutter/flutter and flutter/engine.

The only remaining non-copyright-line differences should now be:
- packages/image_picker/image_picker/LICENSE has an extra license
- packages/google_sign_in/extension_google_sign_in_as_googleapis_auth/LICENSE use "Google LLC" rather than "Google Inc." in the third condition.
51 files changed
tree: 3475c7935ea1983cb9a2953033e4f5b32f1a2d1c
  1. packages/