rust-index: remove one collect when converting back
Turns out this is slightly faster. Sending the results back to Python is still
the most costly (like 75% of the time) of the whole method, but it's about
as fast as it can be now.
hg perf::phases on mozilla-try-2023-03-22
before: 0.267114
after: 0.247101
#require docutils
#require gettext
Test document extraction
$ HGENCODING=UTF-8
$ export HGENCODING
$ { echo C; ls "$TESTDIR/../i18n"/*.po | sort; } | while read PO; do
> LOCALE=`basename "$PO" .po`
> echo "% extracting documentation from $LOCALE"
> LANGUAGE=$LOCALE "$PYTHON" "$TESTDIR/../doc/gendoc.py" >> gendoc-$LOCALE.txt 2> /dev/null || exit
>
> if [ $LOCALE != C ]; then
> if [ ! -f $TESTDIR/test-gendoc-$LOCALE.t ]; then
> echo missing test-gendoc-$LOCALE.t
> fi
> cmp -s gendoc-C.txt gendoc-$LOCALE.txt && echo "** NOTHING TRANSLATED ($LOCALE) **"
> fi
> done; true
% extracting documentation from C
% extracting documentation from da
% extracting documentation from de
% extracting documentation from el
% extracting documentation from fr
% extracting documentation from it
% extracting documentation from ja
% extracting documentation from pt_BR
% extracting documentation from ro
% extracting documentation from ru
% extracting documentation from sv
% extracting documentation from zh_CN
% extracting documentation from zh_TW