Fix x-axis bug in actions.scaleTo

[reissbaker]

Previously if scaling only on the x-axis, the action would never complete.

===:clipboard: PR Checklist :clipboard:===

• 📌 issue exists in github for these changes
• 🔬 existing tests still pass
• 🙈 code conforms to the style guide
• 📐 new tests written and passing / old tests updated with new scenario(s)
• 📄 changelog entry added (or not needed) I think it's not needed for a small bugfix?

==================

Closes #2470

Changes:

Fixes a bug I found in the ScaleTo action, where scaling on the x-axis exclusively may never complete. The isComplete method accidentally tested tx.scale.y against the x-axis, rather than testing tx.scale.x against the x-axis. I wrote the test first, watched it fail, and then fixed the bug and watched the test pass.

It looks like since I'm a first-time contributor I'll need approval from a maintainer to actually run the CI checks, but I pinky swear I ran npm run all locally and it all passed. 😄

[eonarheim]

@reissbaker Thanks for the contribution! This is fantastic!

[reissbaker]

Thanks for the quick merge! :)