x/pkgsite: remove mariusor/littr.go

[mariusor]

What is the URL of the page with the issue?

https://pkg.go.dev/github.com/mariusor/littr.go

What did you expect to see?

I am the owner of mariusor/littr.go, which underwent a rename (to mariusor/go-littr) because the default go tooling has issues with packages whose names end in .go.

I expected that the package gets removed when it dissapears from github.

What did you see instead?

I can still view the version of the package before the rename even though no external packages are importing it.

[jamalc]

Done.