cleanup: replace oneWay with toView

[jdanyow]

We should standardize the internals on toView now that it has landed. Here's one instance, probably others...

https://github.com/aurelia/templating-binding/blob/ebd3dc28b65a9fac15972281afe7078829a9f8b7/src/binding-language.js#L57

We still need to support oneWay but the internals should use toView where possible.

related to https://github.com/aurelia/binding/issues/629

[veikkoeeva]

Is this and the linked ones low-risk changes? :)

[bigopon]

Zero risk i would say :+1:

[veikkoeeva]

Should someone reel this wandering fix in? One place at a time is good enough for making progress. :)

[bigopon]

@veikkoeeva that'd be awesome 😄