web: include alwaysRender on blob error page
Created by: keegancsmith
Not including alwaysRender lead to some toolbar items not showing (such as the download button). An example of a common error page is we don't render images. However, we would still like to include the download button.
Note: We rely on the raw endpoint for the download functionality. For security reasons this will always set the content-type to text/plain. This means when you download the file it will be downloaded as a txt file. We can't support more mime-types unless we can serve the assets on a different domain.
Fixes https://github.com/sourcegraph/sourcegraph/issues/7924