ibuf-ext.el: Fix previous change

* lisp/ibuf-ext.el (ibuffer-generate-filter-groups): Use
`cl-destructuring-bind' instead of `cl-multiple-value-bind', as we
don't want to assume how multiple-values are implemented, and we
know a list is being returned anyway.  Suggested by Stefan Monnier.
1 job for master in 56 minutes and 18 seconds (queued for 1 second)
Status Job ID Name Coverage
failed #4408


Name Stage Failure
test-all Test
Makefile:319: recipe for target 'check-doit' failed
make[2]: *** [check-doit] Error 1
make[2]: Leaving directory '/builds/emacs/emacs/test'
Makefile:294: recipe for target 'check-expensive' failed
make[1]: Leaving directory '/builds/emacs/emacs/test'
make[1]: *** [check-expensive] Error 2
Makefile:959: recipe for target 'check-expensive' failed
make: *** [check-expensive] Error 2
ERROR: Job failed: exit code 1