fdo#73800 fix incorrect separator in function description in Calc

Depending on locale, the function description with arguments did
show incorrect separator(s) for functions with PAIRED_VAR_ARGS.

Change-Id: Ie493a77285360a099e5b07e8360ecb5c6c6c1aec
Reviewed-on: https://gerrit.libreoffice.org/8052
Reviewed-by: Kohei Yoshida <libreoffice@kohei.us>
Tested-by: Kohei Yoshida <libreoffice@kohei.us>