Notebook output renderer picker doesn't use display names

[JacksonKearl]

    "notebookOutputRenderer": [
      {
        "viewType": "github-issue-static-renderer",
        "displayName": "Static Issue Renderer",
        "mimeTypes": [
          "ms-vscode.github-issue-notebook/github-issue"
        ]
      },

[JacksonKearl]

I think at the very least github-issue-static-renderer should be replaced with Static Issue Renderer, and potentially it should be givent higher visual priority over the mimetype. cc @misolori