deps: remove unused deps

[outsideris]

Description of the Change

Remove unused 3 dependencies.

• configstore
  • It introduced in 2137163 . But It appears to have been added by mistake from the beginning.
• through2
  • It was introduced in a81e555 7 years ago for browserify. But I couldn't find where to use it in this commit.
  • It looks like removed in this commit when we drop the browserify.
• watchify
  • It was introduced at c04c1d7 . But I couldn't find where to use it in this commit.
  • This is for browserify. Now we don't use browserify anymore.

[juergba]

@outsideris there is a watch script in package-scripts.js, I suppose it uses watchify for its purpose. I don't think anybody has ever used that script, so could certainly be removed.

[outsideris]

@juergba Did you mean here? I think docs.watch doesn't use watchify.

[juergba]

@outsideris thank you