[bazel.build] Problem with /install/completion

### Page link:

https://bazel.build/install/completion

### Problem description (include actual vs expected text, if applicable):

Recommended installation is via bazelisk, but the autocomplete installation instructions doesn't have that as an option. None of the instructions seem to be suitable for bazelisk.

### Where do you see this issue? (include link to specific section of the page, if applicable)

_No response_

### Any other information you'd like to share?

I found https://github.com/bazelbuild/bazelisk/issues/29, but this should either be implemented or linked from the docs.

Start with the /install/completion page and review the related Bazelisk issue #29 linked in the report. Determine whether the documentation should include Bazelisk autocomplete instructions or link to existing guidance; done means the page clearly supports or directs Bazelisk users.

Written by the indexing model from the issue text.