pgsql: Fix show_incremental_sort_info with force_parallel_mode

Fix show_incremental_sort_info with force_parallel_mode

When executed with force_parallel_mode=regress, the function was exiting
too early and thus failed to print the worker stats. Fixed by making it
more like show_sort_info.

Discussion: https://postgr.es/m/CAPpHfds1waRZ=NOmueYq0sx1ZSCnt+5QJvizT8ndT2=etZEeAQ@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/7d6d82a52493ad47c57662d0ac6758da551e87a5

Modified Files
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src/backend/commands/explain.c | 19 +++++++++++--------
1 file changed, 11 insertions(+), 8 deletions(-)