MobaXterm's apt-cyg/apt-get/"Packages" seems to be unaware that setup.ini is now located one level deeper in x86/setup.ini and x86_64/setup.ini. You can tell that the setup.ini is old because it is trying to retrieve the old version of git-2.8.3-1 (current is git-2.17.0-1). Running MobaXterm's "Packages" icon also gives you a few more details for this error.
The simple (and non-invasive) fix is to replace setup.ini with a newer version. Based on 32-bit (uname -m) and the URL in your error message, you can retrieve your latest setup.ini from here:
http://mirrors.kernel.org/sourceware.../x86/setup.ini
The setup.ini file to overwrite is located in this directory:
/home/mobaxterm/.aptcyg/http%3a%2f%2fmirrors.kernel.org%2fsourceware%2fcygwin
That fixed things for me and I was able to install the current version of git.
Also, regarding cygports (so you don't go down a rabbit hole), looks like the cygports repository has been "removed" and good packages folded into the main cygwin repository, see "Project Update":
https://sourceware.org/cygwinports/
MobaXterm Professional Edition v10.5 Build 3582