[exec.get.compl.sched] Remove spurious @

Author: timsong-cpp

source/exec.tex

@@ -1130,11 +1130,11 @@
 \tcode{envs} is not an empty pack,
 except that \tcode{envs...} is evaluated.
 \item
-Otherwise, \tcode{get_completion_scheduler<@\exposid{completion-fn-tag}@>(q, envs...)}
+Otherwise, \tcode{get_completion_scheduler<\exposid{completion-fn-tag}>(q, envs...)}
 is ill-formed.
 \end{itemize}
 \mandates
-If \tcode{get_completion_scheduler<@\exposid{completion-fn-tag}@>(q, envs...)}
+If \tcode{get_completion_scheduler<\exposid{completion-fn-tag}>(q, envs...)}
 is well-formed,
 its type satisfies \libconcept{scheduler}.