Fix remove special chars from snippet url_to_repo

What does this MR do?

Snippets full_path generation is very special. In order to avoid possible collisions between projects named snippets and the special snippets paths, it adds the char @ to it. Therefore, snippet.url_to_repo will be like: ssh://fran@127.0.0.1:2222/root/test/@snippets/138.git or ssh://fran@127.0.0.1:2222/@snippets/138.git.

Obviously, that path is invalid.

In this MR, we remove the special char @ in url_to_repo in order to generate the snippet ssh urls: ssh://fran@127.0.0.1:2222/root/test/snippets/138.git and ssh://fran@127.0.0.1:2222/snippets/138.git.

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content