Update whatwg-fetch to version ^2.0.3

[kalman]

See #12961

[kalman]

I've tested this with npm test, I don't know what else to do.

[facebook-github-bot]

@kalman I tried to find reviewers for this pull request and wanted to ping them to take another look. However, based on the blame information for the files in this pull request I couldn't find any reviewers. This sometimes happens when the files in the pull request are new or don't exist on master anymore. Is this pull request still relevant? If yes could you please rebase? In case you know who has context on this code feel free to mention them in a comment (one person is fine). Thanks for reading and hope you will continue contributing to the project.

[ide]

Commits like these are deceptively tricky since most of the work is combing through the changelog and making sure it didn't break any behavior currently used, and then trying it in a couple of apps. Can you construct a reproduceable test plan and explain why you're confident in this change?

[kalman]

Yep, understood.

I don't have the time right now to test this super exhaustively though unfortunately :-(

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Maybe the issue has been fixed in a recent release, or perhaps it is not affecting a lot of people. If you think this issue should definitely remain open, please let us know why. Thank you for your contributions.