[animations] Remove unnecessary override

[creativecreatorormaybenot]

reverseTransitionDuration in TransitionRoute is only added in v1.15.3 and Flutter stable is at v1.12.13+hotfix.8.

Thus, the @override annotation should not exist currently (analyzer is complaining).

[shihaohong]

The issue with commenting out the @OverRide annotation here is that it will break the Material transitions as well (tests will fail because the transitions are technically incorrect going in the reverse direction).

cc/ @goderbauer Has a scenario like this ever happened before? The best answer I can come up with is to wait for the reverse duration feature to hit the master branch.

[goderbauer]

What is the failure mode when you use the library with the current stable of Flutter? Is it just the analyzer complaining and the reverseDuration gets ignored in favor of the regular duration? In that case I'd suggest doing nothing and just waiting for the next stable release.

[creativecreatorormaybenot]

@goderbauer I see. So should I close this then?

[goderbauer]

Yeah, I think we should just close this since this has no real impact for users of the package. If the analyzer warning bothers you, we could add a a dart // ignore: to that line with a TODO to remove it when that change hits stable.

[goderbauer]

@shihaohong is adding that // ignore: in #109. I am going to close this PR in favor of that one.