Conditionally link to the SRFI docs on docs.racket-lang.org when rendering PDFs.
Conditionally link to the SRFI docs on docs.racket-lang.org when rendering PDFs.

Closes PR 11804.

mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket