fixup: use \brk{} to deal with overfull hbox

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

Author: dietmarkuehl

source/exec.tex

@@ -6146,7 +6146,7 @@
 \begin{itemdescr}
 \pnum
 The type \exposid{own-env-t} is \tcode{Environment::template
-env_type<decltype(get_env(\linebreak declval<Rcvr>()))>} if that % avoid Overfull
+env_type<decltype(get_env(\brk{}declval<Rcvr>()))>} if that
 qualified-id is valid and denotes a type, \tcode{env<>} otherwise.
 \end{itemdescr}