Some corrections seem to be needed in Reactivity in Depth section

[t0yohei]

When I tried translating to Japanese, I noticed some points need to be corrected in the part of How Vue Tracks These Changes in Reactivity in Depth section.
https://v3.vuejs.org/guide/reactivity.html#how-vue-tracks-these-changes

We mentioned before that in order to have an API that updates a final value when something changes, we’re going to have to set new values when something changes.

In the part above, I think we have to say about function trucking, however, it seems to be said about updating new value.

Track the function that changes it: We do this in a getter within the proxy, called effect

I think the function name is not effect but track.

[skirtles-code]

I'm looking into updating this now. I think there are a few other tweaks required to that section too, so it may take a few days to get this ready for PR.

[Brisstor]

@skirtles-code Since you're working on it, found one more typo here. I'm not sure if you have seen it before, so here it is:

We mentioned before that in order to have an API that updates a final value when something changes, we’re going to have to set new values when something changes. We do this in the handler, in a function called track, where we pass in the target and key.

Suppose there should be prop instead of key.

[skirtles-code]

@Brisstor Thanks.

I'm going to change all the references to prop and key to something else because both of those terms have other meanings in a Vue context and I'd rather avoid any potential for confusion.

Despite the apparent lack of progress I am still working on this. There are a few kinks that are proving difficult to iron out.

[Brisstor]

@skirtles-code Thanks, also I'll be grateful if you mention me after you finish this issue so I would be able to update Russian translation of that section.

[skirtles-code]

@t0yohei @Brisstor. I now have a draft of my proposed changes in #934.

I understand that making large changes like these places a burden on the translators. Hopefully the improvements are worth it. Please feel free to review what I've done and provide any feedback you may have on the PR. Thanks.