docs(config): clarify config help

Description

This MR updates the help for glab config:

1. use host rather than gitlab_uri as host is what is actually used in the config file.
2. replace references to the "old" local config .glab-cli/config/config.yml to .git/glab-cli/config.yml (related to https://gitlab.com/gitlab-org/security/cli/-/merge_requests/13 )

The goal of this MR is to make it less confusing for users to configure glab

Related Issues

Resolves #686 (closed)

How has this been tested?

Viewing help

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation
• Chore (Related to CI or Packaging to platforms)
• Test gap