debugger: align message with Node.js standard

Node.js uses (or will use) _Ctrl+C_ with no spaces. To unify the
messages from inspect with other messages from the REPL and elsewhere,
make that change in node-inspect too.

PR-URL: https://github.com/nodejs/node/pull/38400


Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>