ecpg: Remove trailing period from error message.
This commit improves the ecpg's error message that commit
f576de1db1 updated,
so that it gets rid of trailing period and uppercases the command name
in the error message.
Author: Kyotaro Horiguchi
Reviewed-by: Fujii Masao
Discussion: https://postgr.es/m/
20210819.170315.
1413060634876301811.horikyota.ntt@gmail.com