Fix lookup of gpgconf.exe for GnuPG-[VS-]Desktop

* src/client.cc (get_gpgconf_name): Remove trailing "../" from entries
in possible_names.

gpgconf.exe is looked up relative to the install directory, but the
old relative paths seem to have assumed that the lookup happens relative
to the location of gpgex.dll (i.e. the bin or bin_64 subfolder of the
install directory). Before 9c7ec74d3f79bae72da1f7f1cbeb0509f3ac136a the
faulty relative paths were never used because the lookup first used the
GnuPG install directory retrieved from the registry for finding gpgconf.

• Regression-due-to: 9c7ec74d3f79bae72da1f7f1cbeb0509f3ac136a
• GnuPG-bug-id: T8256