Shortened snippet links didn't include the anchor to the line
### Summary
Here's the example:
https://gitlab.com/gitlab-org/gitlab-ce/snippets/20077#L4759
It should show like:
[$20077#L4759](https://gitlab.com/gitlab-org/gitlab-ce/snippets/20077#L4759)
### Steps to reproduce
Paste `https://gitlab.com/gitlab-org/gitlab-ce/snippets/20077#L4759` and preview it
### What is the current *bug* behavior?
[$20077](https://gitlab.com/gitlab-org/gitlab-ce/snippets/20077)#L4759
### What is the expected *correct* behavior?
[$20077#L4759](https://gitlab.com/gitlab-org/gitlab-ce/snippets/20077#L4759)
### Output of checks
This bug happens on GitLab.com
This was discovered at https://gitlab.com/gitlab-org/gitlab-ce/issues/49640#note_115866033
issue