Remove obsolete comment

I ran into this outdated comment, where `olx.js` and `oli.js` are stated to be used as inputs. This seems not to be the case anymore.

But instead of clearing this comment, I'd rather see the examples _being_ parsed with these externs as inputs. Unfortunately, these files cannot be added directly, as they lack a `goog.provide`. I could update this PR so the files are modified and stored in e.g. `build/examples/src`, ready to be used as inputs. Are you in favor of such a change?

The reason I would like to do so, is that I ran into the exact same problem while making my own custom build.
Shouldn't there be a comment explaining why these 'externs' are under `js` and not `externs`, like the others?