katy-sliders example does not compile on Racket 8.8

[samth]

Current Racket HEAD (as of 1/3/23) has the following error:

[samth@huor:/tmp plt] raco make  -l rsound/examples/katy-sliders
<pkgs>/rsound/rsound/examples/katy-sliders.rkt:296:1: network: expected one of these identifiers: `=' or `<='
  at: <=
  in: (network () (ctr <= (flexloop SONGLEN) (fetch-speed)) (delayed-ctr = (maybe-wrap ctr (fetch-delay) SONGLEN)) (out = (/ (+ (rs-ith/left SONG (floor ctr)) (rs-ith/left SONG (floor delayed-ctr))) 2)))
  parsing context: 
   while parsing network clause rhs
    term: (<= (flexloop SONGLEN) (fetch-speed))
    location: <pkgs>/rsound/rsound/examples/katy-sliders.rkt:297:3
   while parsing network clause
    term: (ctr <= (flexloop SONGLEN) (fetch-speed))
    location: <pkgs>/rsound/rsound/examples/katy-sliders.rkt:297:3
  compilation context...:
   /home/samth/sw/plt/racket/share/pkgs/rsound/rsound/examples/katy-sliders.rkt
  location...:
   /home/samth/sw/plt/racket/share/pkgs/rsound/rsound/examples/katy-sliders.rkt:297:8
  context...:
   /home/samth/sw/plt/racket/collects/syntax/parse/private/runtime-report.rkt:731:0: error/report
   /home/samth/sw/plt/racket/collects/syntax/parse/private/runtime-report.rkt:28:0: call-current-failure-handler

This seems like a regression from 8.7, where it seems to work.

cc @rmculpepper