Thanks for posting to the git for Windows Google group forum.
I'm excited for you as you start your journey using git version control.
To answer your question, "what is the wish applcation?" Wish is a graphical shell for the Tk/Tcl programming language used to develop graphical user interfaces on Linux and other *nix operating systems.
See:
https://en.wikipedia.org/wiki/Wish_(Unix_shell)
https://www.tcl.tk/man/tcl/UserCmd/wish.htm
The link that you pasted in your question points to an issue that was created on the GitHub page for this open source project called "git for Windows"
https://github.com/git-for-windows/git/issues/737#issuecomment-212289591
The maintainer of this open source project, Johannes Schindelin explains that Wish is the application that renders the Git GUI which comes with git
https://git-scm.com/docs/git-gui
So in short, you don't want to remove this, it's a feature not a bug. It may be confusing, because you probably expected the task bar to indicate that the git gui was open, sorry. Just think if you we're running a Windows batch script, the icon would say cmd, even tho your script does something else.
Git was originally written by Linus Torvalds as the version control for linux, the open source operating system that he invented
https://www.linuxfoundation.org/blog/10-years-of-git-an-interview-with-git-creator-linus-torvalds/
Therefore a lot of things had to be ported to Windows and so they are sometimes a little different from what we're used to on Windows.
If you are really bothered by the word icon, consider using a different frontend like tortoiseGit, that will be much more familiar to Windows users
One last thing, consider being very nice to the maintainers of open source software. They are often volunteering or are paid part-time to maintain these projects, and they have to deal with unreasonable expectations sometimes from users. Remember, you are getting something for free, not paying for it, so try to be grateful. Otherwise an open source maintainer can just decide one day to give up. Consider taking that extra step of contributing back. If everyone did this, the burden would be so much lower. If you have time consider reading this report on the state of open source