Rename snippet blob raw route

What does this MR do?

This MR renames the recently added raw personal snippet route to be consistent with the project variation.

Currently it's setup to have the named route of snippet_raw

After this change, the routes will look like:

• ProjectSnippet raw blob route: namespace_project_snippet_blob_raw_*
• PersonalSnippet raw blob route: snippet_blob_raw_*

Currently neither of the named routes are being used, but they will be as part of #217807 (closed).

This change will help to differentiate between the existing/old raw snippet route raw_snippet_*

Closes #224516 (closed)

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Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.