Remove `inferior-sly.el` fix broken dependencies on `sly-parent-mode'

* contrib/inferior-sly.el: removed.

* contrib/sly-sprof.el (sly-sprof-browser-mode-map)
(sly-sprof-browser-mode): Start `sly-mode' minor mode. Don't use
`sly-parent-mode'.p

* contrib/sly-trace-dialog.el (sly-trace-dialog-mode-map)
(sly-trace-dialog-mode): Start `sly-mode'
minor mode. Don't use `sly-parent-mode'.