[exec.sysctxrepl.psb] Add \tcode for execute (#8176)

Author: Andreas-Krug

source/exec.tex

@@ -8676,7 +8676,7 @@
 then for each $i$ in \range{0}{n},
 there is exactly one call to \tcode{r.execute($i$, $i$ + 1)}.
 \item
-All calls to execute on \tcode{r} happen before
+All calls to \tcode{execute} on \tcode{r} happen before
 the call to either \tcode{set_value}, \tcode{set_error}, or \tcode{set_stopped}
 on \tcode{r}.
 \item