No longer automatically open web browser when doing local views

What does this MR do and why?

When Hugo automatically opens a web browser, it takes window focus from anything else you're doing, whether from within the web browser or in another application.

I frequently have the correct URL already loaded locally, so having the browser re-open the docs landing page every time I run make view isn't necessary.

Because the correct URL to the docs landing page is printed to the terminal and easily followed, I don't think we should automatically open the browser at all and leave it to the individual.

CC @gitlab-org/technical-writing/tw-docops

How to set up and validate locally

1. Configure a local GitLab Docs environment.
2. Run make view. The web browser automatically opens.
3. Check out this branch.
4. Run make view. The web browser no longer automatically opens.

Merge request acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this merge request.