fixup: use \brk{} for overfull hbox

Co-authored-by: Jan Schultke <[email protected]>

Author: dietmarkuehl

source/exec.tex

@@ -6223,7 +6223,7 @@
 \tcode{\libconcept{invocable}<Fn>} and
 \tcode{\libconcept{constructible_from}<Fn, Init>} are modeled,
 \tcode{stop_token_type::callback_type<Fn>} models
-\tcode{\exposid{stoppable-callback-for}<Fn,\linebreak stop_token_type, % avoid Overfull
+\tcode{\exposconcept{stoppable-callback-for}<Fn,\brk{} stop_token_type, Init>}.
 Init>}.
 \end{itemize}