docs: correct the snippet command docs to only mention create

Uma Chandranrequested to merge
uc/add-snippet-examples into main

Description

Updates the glab snippet docs to remove references to view and manage as it looks like the only command available is create. Adds in a line to point users to the GitLab UI or API instead

Related issues and merge requests

https://gitlab.com/gitlab-org/gitlab/-/work_items/628257+

Documentation

If this MR adds or updates CLI command documentation, follow the conventions in the GitLab CLI (glab) documentation style guide, run make gen-docs, and commit the updated files in docs/source/.

Merge request reports