Fix x-axis direction in Offset.direction doc

[thgoebel]

Description

This PR fixes the doc comment for Offset.direction to correctly say that the x-axis goes to the right (rather than to the left).

Related Issues

None that I am aware of. Rather than opening an issue for something this small, I'm sending a PR right away.

Tests

I added the following tests:

N/A

Checklist

Before you create this PR confirm that it meets all requirements listed below by checking the relevant checkboxes ([x]). This will ensure a smooth and quick review process.

• I read the contributor guide and followed the process outlined there for submitting PRs.
• I signed the CLA.
• I read and followed the C++, Objective-C, Java style guides for the engine.
• I read the tree hygiene wiki page, which explains my responsibilities.
• I updated/added relevant documentation.
• All existing and new tests are passing.
• I am willing to follow-up on review comments in a timely manner.

ad style guide: I haven't read it yet, but didn't change any code
ad tests: I didn't run them since I didn't change any code

Breaking Change

Did any tests fail when you ran them? Please read handling breaking changes.

I didn't run the tests, but I'd assume "No".

• No, no existing tests failed, so this is not a breaking change.
• Yes, this is a breaking change. If not, delete the remainder of this section.
  • I wrote a design doc: https://flutter.dev/go/template Replace this with a link to your design doc's short link
  • I got input from the developer relations team, specifically from: Replace with the names of who gave advice
  • I wrote a migration guide: https://flutter.dev/go/breaking-changes-template Replace this with a link to a pull request that adds the migration guide to https://flutter.dev/docs/release/breaking-changes

[flutter-dashboard]

It looks like this pull request may not have tests. Please make sure to add tests before merging. If you need an exemption to this rule, contact Hixie on the #hackers channel in Chat.

Reviewers: Read the Tree Hygiene page and make sure this patch meets those guidelines before LGTMing.

[cbracken]

Yikes! Good catch! Thanks for the fix!