Always set CLOSURE_NO_DEPS to true

Because we generate our own deps file (`ol-deps.js`), we already set `CLOSURE_NO_DEPS` to `true` for the hosted examples in `raw` mode.

In `whitespace` mode the Closure Library also attempts to load `deps.js`. This is not needed, and not desired because it causes a 404. The issue was reported by @ThomasG77 in #667.

This PR fixes it by setting `CLOSURE_NO_DEPS` to `true` for any mode - it has no effect at all for the `simple` and `advanced` modes.