Fix glacier command

[camelid]

It was fetching the HTML rather than the raw source;
see rust-lang/glacier#530 for an example.

[kellda]

cc rust-lang/glacier#231

[camelid]

@Mark-Simulacrum Could you review this? Thanks!

[camelid]

Thanks! Looking forward to using the command now :)

[camelid]

Hmm, it doesn't seem to be working: rust-lang/rust#78632 (comment)

[kellda]

Why did you sent the command twice ?

[camelid]

Because the first time it didn't work – you need to include /rust-play/ in the Gist URL, which I had not done. That should probably be fixed too.

@Mark-Simulacrum did you see anything in the logs that would explain why rustbot silently failed?

[kellda]

It probably failed because it wasn't able to recreate a branch with the same name. (The branch having been created by your first command)

See rust-lang/glacier#231 (comment) and rust-lang/glacier#231 (comment)

[Mark-Simulacrum]

I don't have time right now to track down logs unfortunately, but @kellda's theory looks like the right one.