Remove Flow typings from Schedule.js

[alexeyraspopov]

As described in #13582, this file needs to be as close to ES5 as possible. Flow pragma (@flow) was deleted but there was still a single function signature. Removing it in this PR.

Not sure about what should be done to the export statement in the end though.

[sizebot]

Details of bundled changes.

Comparing: d92114b...73e9081

schedule

File	Filesize Diff	Gzip Diff	Prev Size	Current Size	Prev Gzip	Current Gzip	ENV
schedule.development.js	n/a	n/a	0 B	19.17 KB	0 B	5.74 KB	UMD_DEV
schedule.production.min.js	n/a	n/a	0 B	3.16 KB	0 B	1.53 KB	UMD_PROD

Generated by 🚫 dangerJS

[gaearon]

We want to keep export / import since that part would be necessary for ESM. We'll just compile it alone for UMD later.

[gaearon]

We should probably tweak this to do the checking for us.
https://github.com/facebook/react/blob/master/scripts/shared/pathsByLanguageVersion.js

[NE-SmallTown]

We should probably tweak this to do the checking for us.

You mean add 'packages/schedule/src/*.js' to es5Paths in pathsByLanguageVersion.js?

We'll just compile it alone for UMD later.

But the main field of the package.json of schedule refer to './src/index' rather than './npm/index', I'm a little confused here